# Programming with SQL Relay using the C API

- Compiling an SQL Relay Client Program
- Establishing a Session
- Executing Queries
- Commits and Rollbacks
- Temporary Tables
- Catching Errors
- Substitution and Bind Variables
- Re-Binding and Re-Executing
- Accessing Fields in the Result Set
- Dealing With Large Result Set
- Cursors
- Getting Column Information
- Stored Procedures
- Caching The Result Set
- Suspending and Resuming Sessions
- Getting the Last Insert ID

## Compiling an SQL Relay Client Program

When writing an SQL Relay client program using the C API, you need to include the sqlrclientwrapper.h file.

>     #include <sqlrelay/sqlrclientwrapper.h>

You'll also need to link against the sqlrclientwrapper, sqlrclient and rudiments libraries.

On Linux and Unix, the header files are usually found under /usr/local/firstworks/include and the libraries are usually found in /usr/local/firstworks/lib.

On Windows, the header files are usually found under C:\Program Files\Firstworks\include, the .lib files are usually found under C:\Program Files\Firstworks\lib and the .dll files are usually found under C:\Program Files\Firstworks\bin.

The command to compile your .c file to object code will look something like this (assuming you're using the GNU C compiler on Linux or Unix):

>     gcc -I/usr/local/firstworks/include -c myprogram.c

The command to compile your .o file to an executable will look something like this (assuming you're using the GNU C++ compiler on Linux or Unix):

>     g++ -o myprogram myprogram.o -L/usr/local/firstworks/lib -lsqlrclientwrapper -lsqlrclient -lrudiments

Note that g++ was used to link, not gcc. You could alternatively link using gcc like this:

>     gcc -o myprogram myprogram.o -L/usr/local/firstworks/lib -lsqlrclientwrapper -lsqlrclient -lrudiments -lstdc++

When using the C API, it is important to compile the .c files to object code using the C compiler before linking them using the C++ compiler. Compiling/Linking in one step using the C++ compiler the will most likely fail as it will generate C++ style symbols for function calls which will not be resolved in the sqlrclientwrapper library since it contains C style function symbols. Compiling to object code using the C compiler as a seperate step ensures that C style symbols will be generated for function calls.

## Establishing a Session

To use SQL Relay, you have to identify the connection that you intend to use.

>     #include <sqlrelay/sqlrclientwrapper.h>
>     #include <stdio.h>

>     main() {

>             sqlrcon      con=sqlrcon_alloc("sqlrserver",9000,"/tmp/example.socket","user","password",0,1);

>             ... execute some queries ...

>             sqlrcon_free(con);
>     }

After calling the constructor, a session is established when the first query is run.

For the duration of the session, the client occupies one of the database connections, so care should be taken to minimize the length of a session.

Sessions can also be encrypted and authenticated using Kerberos/Active Directory or TLS/SSL. The sqlrcon_enableKerberos() function is provided to enable Kerberos/Active Directory encryption and authentication and the sqlrcon_enableTls() function is provided to enable TLS/SSL encryption and authentication. The sqlrcon_disableEncryption() function is provided to disable any previously enabled encryption.

See the C API reference for information about these functions and the SQL Relay Configuration Guide for more information about Kerberos/Active Directory and TLS/SSL configurations. In particular, note that user and password are not typically used when using Kerberos/AD.

## Executing Queries

Call sqlrcur_sendQuery() or sqlrcur_sendFileQuery() to run a query.

>     #include <sqlrelay/sqlrclientwrapper.h>
>     #include <stdio.h>

>     main() {

>             sqlrcon      con=sqlrcon_alloc("sqlrserver",9000,"/tmp/example.socket","user","password",0,1);
>             sqlrcur      cur=sqlrcur_alloc(con);

>             sqlrcur_sendQuery(cur,"select * from my_table");

>             ... do some stuff that takes a short time ...

>             sqlrcur_sendFileQuery(cur,"/usr/local/myprogram/sql","myquery.sql");
>             sqlrcon_endSession(con);

>             ... do some stuff that takes a long time ...

>             sqlrcur_sendQuery(cur,"select * from my_other_table");
>             sqlrcon_endSession(con);

>             ... process the result set ...

>             sqlrcur_free(cur);
>             sqlrcon_free(con);
>     }

Note the call to sqlrcon_endSession() after the call to sqlrcur_sendFileQuery(). Since the program does some stuff that takes a long time between that query and the next, ending the session there allows another client an opportunity to use that database connection while your client is busy. The next call to sqlrcur_sendQuery() establishes another session. Since the program does some stuff that takes a short time between the first two queries, it's OK to leave the session open between them.

## Commits and Rollbacks

If you need to execute a commit or rollback, you should use the sqlrcon_commit() and sqlrcon_rollback() functions rather than sending a "commit" or "rollback" query. There are two reasons for this. First, it's much more efficient to call the functions. Second, if you're writing code that can run on transactional or non-transactional databases, some non-transactional databases will throw errors if they receive a "commit" or "rollback" query, but by calling the sqlrcon_commit() and sqlrcon_rollback() functions you instruct the database connection daemon to call the commit and rollback API functions for that database rather than issuing them as queries. If the API's have no commit or rollback functions, the calls do nothing and the database throws no error.

You can also turn Autocommit on or off with the sqlrcon_autoCommitOn() and sqlrcon_autoCommitOff() functions. When Autocommit is on, the database performs a commit after each successful DML or DDL query. When Autocommit is off, the database commits when the client instructs it to, or (by default) when a client disconnects. For databases that don't support Autocommit, sqlrcon_autoCommitOn() and sqlrcon_autoCommitOff() have no effect.

## Temporary Tables

Some databases support temporary tables. That is, tables which are automatically dropped or truncated when an application closes its connection to the database or when a transaction is committed or rolled back.

For databases which drop or truncate tables when a transaction is committed or rolled back, temporary tables work naturally.

However, for databases which drop or truncate tables when an application closes its connection to the database, there is an issue. Since SQL Relay maintains persistent database connections, when an application disconnects from SQL Relay, the connection between SQL Relay and the database remains, so the database does not know to drop or truncate the table. To remedy this situation, SQL Relay parses each query to see if it created a temporary table, keeps a list of temporary tables and drops (or truncates them) when the application disconnects from SQL Relay. Since each database has slightly different syntax for creating a temporary table, SQL Relay parses each query according to the rules for that database.

In effect, temporary tables should work when an application connects to SQL Relay in the same manner that they would work if the application connected directly to the database.

## Catching Errors

If your call to sqlrcur_sendQuery() or sqlrcur_sendFileQuery() returns a 0, the query failed. You can find out why by calling sqlrcur_errorMessage().

>     #include <sqlrelay/sqlrclientwrapper.h>
>     #include <stdio.h>

>     main() {

>             sqlrcon      con=sqlrcon_alloc("sqlrserver",9000,"/tmp/example.socket","user","password",0,1);
>             sqlrcur      cur=sqlrcur_alloc(con);

>             if (!sqlrcur_sendQuery(cur,"select * from my_nonexistant_table")) {
>                     printf("%s\n",sqlrcur_errorMessage(cur));
>             }

>             sqlrcur_free(cur);
>             sqlrcon_free(con);
>     }

## Substitution and Bind Variables

Programs rarely execute fixed queries. More often than not, some part of the query is dynamically generated. The SQL Relay API provides functions for making substitutions and binds in those queries.

For a detailed discussion of substitutions and binds, see this document.

Rather than just calling sendQuery() you call prepareQuery(), substitution(), inputBind() and executeQuery(). If you using queries stored in a file, you can call prepareFileQuery() instead of prepareQuery().

When passing a floating point number in as a bind or substitution variable, you have to supply precision and scale for the number. See this page for a discussion of precision and scale.

>     #include <sqlrelay/sqlrclientwrapper.h>

>     main() {

>             sqlrcon      con=sqlrcon_alloc("sqlrserver",9000,"/tmp/example.socket","user","password",0,1);
>             sqlrcur      cur=sqlrcur_alloc(con);

>             sqlrcur_prepareQuery(cur,"select * from mytable $(whereclause)")
>             sqlrcur_substitution(cur,"whereclause","where stringcol=:stringval and integercol>:integerval and floatcol>floatval");
>             sqlrcur_inputBind(cur,"stringval","true");
>             sqlrcur_inputBind(cur,"integerval",10);
>             sqlrcur_inputBind(cur,"floatval",1.1,2,1);
>             sqlrcur_executeQuery(cur);

>             ... process the result set ...

>             sqlrcur_free(cur);
>             sqlrcon_free(con);
>     }

If you are curious how many bind variables have been declared in a query, you can call countBindVariables() after preparing the query.

If you're using a database with an embedded procedural language, you may want to retrieve data from function calls. To facilitate this, SQL Relay provides functions for defining and retrieving output bind variables.

>     #include <sqlrelay/sqlrclientwrapper.h>

>     main() {

>             sqlrcon      con=sqlrcon_alloc("sqlrserver",9000,"/tmp/example.socket","user","password",0,1);
>             sqlrcur      cur=sqlrcur_alloc(con);

>             sqlrcur_prepareQuery(cur,"begin  :result1:=addTwoIntegers(:integer1,:integer2);  :result2=addTwoFloats(:float1,:float2);  :result3=convertToString(:integer3); end;");
>             sqlrcur_inputBind(cur,"integer1",10);
>             sqlrcur_inputBind(cur,"integer2",20);
>             sqlrcur_inputBind(cur,"float1",1.1,2,1);
>             sqlrcur_inputBind(cur,"float2",2.2,2,1);
>             sqlrcur_inputBind(cur,"integer3",30);
>             sqlrcur_defineOutputBindInteger(cur,"result1");
>             sqlrcur_defineOutputBindDouble(cur,"result2");
>             sqlrcur_defineOutputBindString(cur,"result3",100);
>             sqlrcur_executeQuery(cur);
>             int64_t    result1=sqlrcur_getOutputBindInteger(cur,"result1");
>             double     result2=sqlrcur_getOutputBindDouble(cur,"result2");
>             char       *result3=sqlrcur_getOutputBindString(cur,"result3");
>             sqlrcon_endSession(con);

>             ... do something with the result ...

>             sqlrcur_free(cur);
>             sqlrcon_free(con);
>     }

The getOutputBindString() function returns a NULL value as an empty string. If you would it to come back as a NULL instead, you can call the getNullsAsNulls() function. To revert to the default behavior, you can call getNullsAsEmptyStrings().

You can insert data into BLOB and CLOB columns using the inputBindBlob(), inputBindClob() functions.

>     #include <sqlrelay/sqlrclientwrapper.h>

>     main() {

>             sqlrcon      con=sqlrcon_alloc("sqlrserver",9000,"/tmp/example.socket","user","password",0,1);
>             sqlrcur      cur=sqlrcur_alloc(con);

>             sqlrcur_executeQuery(cur,"create table images (image blob, description clob)");

>             unsigned char   imagedata[40000];
>             unsigned long   imagelength;

>             ... read an image from a file into imagedata and the length of the
>                     file into imagelength ...

>             unsigned char   description[40000];
>             unsigned long   desclength;

>             ... read a description from a file into description and the length of
>                     the file into desclength ...

>             sqlrcur_prepareQuery(cur,"insert into images values (:image,:desc)");
>             sqlrcur_inputBindBlob(cur,"image",imagedata,imagelength);
>             sqlrcur_inputBindClob(cur,"desc",description,desclength);
>             sqlrcur_executeQuery(cur);

>             sqlrcur_free(cur);
>             sqlrcon_free(con);
>     }

Likewise, you can retreive BLOB or CLOB data using defineOutputBindBlob()/getOutputBindBlob() and defineOutputBindClob()/getOutputBindClob().

>     #include <sqlrelay/sqlrclientwrapper.h>

>     main() {

>             sqlrcon      con=sqlrcon_alloc("sqlrserver",9000,"/tmp/example.socket","user","password",0,1);
>             sqlrcur      cur=sqlrcur_alloc(con);

>             sqlrcur_prepareQuery(cur,"begin  select image into :image from images;  select description into :desc from images;  end;");
>             sqlrcur_defineOutputBindBlob(cur,"image");
>             sqlrcur_defineOutputBindClob(cur,"desc");
>             sqlrcur_executeQuery(cur);

>             char    *image=sqlrcur_getOutputBindBlob(cur,"image");
>             long    imagelength=sqlrcur_getOutputBindLength(cur,"image");

>             char    *desc=sqlrcur_getOutputBindClob(cur,"desc");
>             char    *desclength=sqlrcur_getOutputBindLength(cur,"desc");

>             sqlrcon_endSession(con);

>             ... do something with image and desc ...

>             sqlrcur_free(cur);
>             sqlrcon_free(con);
>     }

Sometimes it's convenient to bind a bunch of variables that may or may not actually be in the query. For example, if you are building a web based application, it may be easy to just bind all the form variables/values from the previous page, even though some of them don't appear in the query. Databases usually generate errors in this case. Calling validateBinds() just prior to calling executeQuery() causes the API to check the query for each bind variable before actually binding it, preventing those kinds of errors. You can also call validBind() to see if a specific variable is valid. However there is a performance cost associated with calling validateBinds() and validBind().

## Re-Binding and Re-Execution

Another feature of the prepare/bind/execute paradigm is the ability to prepare, bind and execute a query once, then re-bind and re-execute the query over and over without re-preparing it. If your backend database natively supports this paradigm, you can reap a substantial performance improvement.

>     #include <sqlrelay/sqlrclientwrapper.h>
>     #include <stdio.h>

>     main() {

>             sqlrcon      con=sqlrcon_alloc("sqlrserver",9000,"/tmp/example.socket","user","password",0,1);
>             sqlrcur      cur=sqlrcur_alloc(con);

>             sqlrcur_prepareQuery(cur,"select * from mytable where mycolumn>:value");
>             sqlrcur_inputBindLong(cur,"value",1);
>             sqlrcur_executeQuery(cur);

>             ... process the result set ...

>             sqlrcur_clearBinds(cur);
>             sqlrcur_inputBindLong(cur,"value",5);
>             sqlrcur_executeQuery(cur);

>             ... process the result set ...

>             sqlrcur_clearBinds(cur);
>             sqlrcur_inputBindLong(cur,"value",10);
>             sqlrcur_executeQuery(cur);

>             ... process the result set ...

>             sqlrcur_free(cur);
>             sqlrcon_free(con);
>     }

## Accessing Fields in the Result Set

The sqlrcur_rowCount(), sqlrcur_colCount(), sqlrcur_getFieldByName() and sqlrcur_getFieldByIndex() functions are useful for processing result sets.

>     #include <sqlrelay/sqlrclientwrapper.h>
>     #include <stdio.h>

>     main() {

>             int        row,col;

>             sqlrcon      con=sqlrcon_alloc("sqlrserver",9000,"/tmp/example.socket","user","password",0,1);
>             sqlrcur      cur=sqlrcur_alloc(con);

>             sqlrcur_sendQuery(cur,"select * from my_table");
>             sqlrcon_endSession(con);

>             for (row=0; row<sqlrcur_rowCount(cur); row++) {
>                     for (col=0; col<sqlrcur_colCount(cur); col++) {
>                             printf("%s,",sqlrcur_getFieldByIndex(cur,row,col));
>                     }
>                     printf("\n");
>             }

>             sqlrcur_free(cur);
>             sqlrcon_free(con);
>     }

The sqlrcur_getFieldByName() and sqlrcur_getFieldByIndex() functions return strings. If you would like to get a field as a long or double, you can use sqlrcur_getFieldAsLongByName()/sqlrcur_getFieldAsLongByIndex() and sqlrcur_getFieldAsDoubleByName()/sqlrcur_getFieldAsDoubleByIndex().

You can also use sqlrcur_getRow() which returns a NULL-terminated array of the fields in the row.

>     #include <sqlrelay/sqlrclientwrapper.h>
>     #include <stdio.h>

>     main() {

>             int        row,col;

>             sqlrcon      con=sqlrcon_alloc("sqlrserver",9000,"/tmp/example.socket","user","password",0,1);
>             sqlrcur      cur=sqlrcur_alloc(con);

>             sqlrcur_sendQuery(cur,"select * from my_table");
>             sqlrcon_endSession(con);

>             for (row=0; row<sqlrcur_rowCount(cur); row++) {
>                     char    **rowarray=sqlrcur_getRow(cur,row);
>                     for (col=0; col<sqlrcur_colCount(cur); col++) {
>                             printf("%s,",rowarray[col]);
>                     }
>                     printf("\n");
>             }

>             sqlrcur_free(cur);
>             sqlrcon_free(con);
>     }

The sqlrcur_getFieldByIndex(), sqlrcur_getFieldByName() and sqlrcur_getRow() functions return NULL fields as empty strings. If you would like them to come back as NULL's instead, you can call the sqlrcur_getNullsAsNulls() function. To revert to the default behavior, you can call sqlrcur_getNullsAsEmptyStrings().

If you want to access the result set, but don't care about the column information (column names, types or sizes) and don't mind getting fields by their numeric index instead of by name, you can call the sqlrcur_dontGetColumnInfo() function prior to executing your query. This can result in a performance improvement, especially when many queries with small result sets are executed in rapid succession. You can call sqlrcur_getColumnInfo() again later to turn off this feature.

## Dealing With Large Result Sets

SQL Relay normally buffers the entire result set. This can speed things up at the cost of memory. With large enough result sets, it makes sense to buffer the result set in chunks instead of all at once.

Use sqlrcur_setResultSetBufferSize() to set the number of rows to buffer at a time. Calls to sqlrcur_getRow(), sqlrcur_getFieldByIndex() and sqlrcur_getFieldByName() cause the chunk containing the requested field to be fetched. Rows in that chunk are accessible but rows before it are not.

For example, if you setResultSetBufferSize(5) and execute a query that returns 20 rows, rows 0-4 are available at once, then rows 5-9, then 10-14, then 15-19. When rows 5-9 are available, getFieldByIndex(0,0) will return NULL and getFieldByIndex(11,0) will cause rows 10-14 to be fetched and return the requested value.

When buffering the result set in chunks, don't end the session until after you're done with the result set.

If you call sqlrcur_setResultSetBufferSize() and forget what you set it to, you can always call sqlrcur_getResultSetBufferSize().

When buffering a result set in chunks, the sqlrcur_rowCount() function returns the number of rows returned so far. The sqlrcur_firstRowIndex() function returns the index of the first row of the currently buffered chunk.

>     #include <sqlrelay/sqlrclientwrapper.h>
>     #include <stdio.h>

>     main() {

>             int     done=0;
>             int     row=0;
>             int     col;
>             char    *field;

>             sqlrcon      con=sqlrcon_alloc("sqlrserver",9000,"/tmp/example.socket","user","password",0,1);
>             sqlrcur      cur=sqlrcur_alloc(con);

>             sqlrcur_setResultSetBufferSize(cur,5);

>             sqlrcur_sendQuery(cur,"select * from my_table");

>             while (!done) {
>                     for (col=0; col<sqlrcur_colCount(cur); col++) {
>                             if (field=sqlrcur_getFieldByIndex(cur,row,col)) {
>                                     printf("%s,",field);
>                             } else {
>                                     done=1;
>                             }
>                     }
>                     printf("\n");
>                     row++;
>             }

>             sqlrcur_sendQuery(cur,"select * from my_other_table");

>             ... process this query's result set in chunks also ...

>             sqlrcur_setResultSetBufferSize(cur,0);

>             sqlrcur_sendQuery(cur,"select * from my_third_table");

>             ... process this query's result set all at once ...

>             sqlrcon_endSession(con);

>             sqlrcur_free(cur);
>             sqlrcon_free(con);
>     }

## Cursors

Cursors make it possible to execute queries while processing the result set of another query. You can select rows from a table in one query, then iterate through its result set, inserting rows into another table, using only 1 database connection for both operations.

For example:

>     #include <sqlrelay/sqlrclientwrapper.h>

>     main() {

>             sqlrcon      con;
>             sqlrcur      cursor1;
>             sqlrcur      cursor2;
>             int          index;

>             con=new sqlrcon_alloc("sqlrserver",9000,"/tmp/example.socket","user","password",0,1);
>             cursor1=new sqlrcur_alloc(con);
>             cursor2=new sqlrcur_alloc(con);

>             sqlrcur_setResultSetBufferSize(cursor1,10);
>             sqlrcur_sendQuery(cursor1,"select * from my_huge_table");

>             index=0;
>             while (!sqlrcur_endOfResultSet(cursor1)) {
>                     sqlrcur_prepareQuery(cursor2,"insert into my_other_table values (:1,:2,:3)");
>                     sqlrcur_inputBindString(cursor2,"1",sqlrcur_getFieldByIndex(cursor1,index,1));
>                     sqlrcur_inputBindString(cursor2,"2",sqlrcur_getFieldByIndex(cursor1,index,2));
>                     sqlrcur_inputBindString(cursor2,"3",sqlrcur_getFieldByIndex(cursor1,index,3));
>                     sqlrcur_executeQuery(cursor2);
>             }

>             sqlrcur_free(cursor2);
>             sqlrcur_free(cursor1);
>             sqlrcon_free(con);
>     }

If you are using stored procedures with Oracle, a stored procedure can execute a query and return a cursor. A cursor bind variable can then retrieve that cursor. Your program can retrieve the result set from the cursor. All of this can be accomplished using defineOutputBindCursor(), getOutputBindCursor() and fetchFromOutputBindCursor().

>     #include <sqlrelay/sqlrclientwrapper.h>
>     #include <stdio.h>

>     main() {

>             int        i,j;

>             sqlrcon         con=sqlrcon_alloc("sqlrserver",9000,"/tmp/example.socket","user","password",0,1);
>             sqlrcur         cur=sqlrcur_alloc(con);

>             sqlrcur_prepareQuery(cur,"begin  :curs:=sp_mytable; end;");
>             sqlrcur_defineOutputBindCursor(cur,"curs");
>             sqlrcur_executeQuery(cur);

>             sqlrcur         bindcur=sqlrcur_getOutputBindCursor(cur,"curs");
>             sqlrcur_fetchFromBindCursor(bindcur);

>             // print fields from table
>             for (i=0; i<sqlrcur_rowCount(bindcur); i++) {
>                     for (j=0; j<sqlrcur_colCount(bindcur); j++) {
>                             printf("%s,",sqlrcur_getFieldByIndex(bindcur,i,j));
>                     }
>                     printf("\n");
>             }

>             sqlrcur_free(bindcur);

>             sqlrcur_free(cur);
>             sqlrcon_free(con);
>     }

The number of cursors simultaneously available per-connection is set at compile time and defaults to 5.

## Getting Column Information

For each column, the API supports getting the name, type and length of each field. All databases support these attributes. The API also supports getting the precision, scale (see this page for a discussion of precision and scale), length of the longest field, and whether the column is nullable, the primary key, unique, part of a key, unsigned, zero-filled, binary, or an auto-incrementing field. However, not all databases support these attributes. If a database doesn't support an attribute, it is always returned as false.

>     #include <sqlrelay/sqlrclientwrapper.h>
>     #include <stdio.h>

>     main() {

>             int        i;

>             sqlrcon      con=sqlrcon_alloc("sqlrserver",9000,"/tmp/example.socket","user","password",0,1);
>             sqlrcur      cur=sqlrcur_alloc(con);

>             sqlrcur_sendQuery(cur,"select * from my_table");
>             sqlrcon_endSession(con);

>             for (i=0; i<sqlrcur_colCount(cur); i++) {
>                     printf("Name:          %s\n",sqlrcur_getColumnName(cur,i));
>                     printf("Type:          %s\n",sqlrcur_getColumnType(cur,i));
>                     printf("Length:        %d\n",sqlrcur_getColumnLength(cur,i));
>                     printf("Precision:     %d\n",sqlrcur_getColumnPrecision(cur,i));
>                     printf("Scale:         %d\n",sqlrcur_getColumnScale(cur,i));
>                     printf("Longest Field: %d\n",sqlrcur_getLongest(cur,i));
>                     printf("Nullable:      %d\n",sqlrcur_getColumnIsNullable(cur,i));
>                     printf("Primary Key:   %d\n",sqlrcur_getColumnIsPrimaryKey(cur,i));
>                     printf("Unique:        %d\n",sqlrcur_getColumnIsUnique(cur,i));
>                     printf("Part of Key:   %d\n",sqlrcur_getColumnIsPartOfKey(cur,i));
>                     printf("Unsigned:      %d\n",sqlrcur_getColumnIsUnsigned(cur,i));
>                     printf("Zero Filled:   %d\n",sqlrcur_getColumnIsZeroFilled(cur,i));
>                     printf("Binary:        %d\n",sqlrcur_getColumnIsBinary(cur,i));
>                     printf("Auth Increment:%d\n",sqlrcur_getColumnIsAutoIncrement(cur,i));
>                     printf("\n");
>             }

>             sqlrcur_free(cur);
>             sqlrcon_free(con);
>     }

Some databases force column names to upper case, others force column names to lower case, and others still support mixed-case column names. Sometimes, when migrating between databases, you can run into trouble. You can use upperCaseColumnNames() and lowerCaseColumnNames() to cause column names to be converted to upper or lower case, or you can use mixedCaseColumnNames() to cause column names to be returned in the same case as they are defined in the database.

>     #include <sqlrelay/sqlrclientwrapper.h>
>     #include <stdio.h>

>     main() {

>             int        i;

>             sqlrcon         con=sqlrcon_alloc("sqlrserver",9000,"/tmp/example.socket","user","password",0,1);
>             sqlrcur         cur=sqlrcur_alloc(con);

>             // column names will be forced to upper case
>             sqlrcur_upperCaseColumnNames(cur);
>             sqlrcur_endQuery(cur,"select * from my_table");
>             sqlrcon_endSession(con);

>             for (i=0; i<sqlrcur_colCount(cur); i++) {
>                     printf("Name:   %s\n",sqlrcur_getColumnName(cur,i));
>             }

>             // column names will be forced to lower case
>             sqlrcur_lowerCaseColumnNames(cur);
>             sqlrcur_endQuery(cur,"select * from my_table");
>             sqlrcon_endSession(con);

>             for (i=0; i<sqlrcur_colCount(cur); i++) {
>                     printf("Name:   %s\n",sqlrcur_getColumnName(cur,i));
>             }

>             // column names will be the same as they are in the database
>             sqlrcur_mixedCaseColumnNames(cur);
>             sqlrcur_endQuery(cur,"select * from my_table");
>             sqlrcon_endSession(con);

>             for (i=0; i<sqlrcur_colCount(cur); i++) {
>                     printf("Name:   %s\n",sqlrcur_getColumnName(cur,i));
>             }

>             sqlrcur_free(cur);
>             sqlrcon_free(con);
>     }

## Stored Procedures

Many databases support stored procedures. Stored procedures are sets of queries and procedural code that are executed inside of the database itself. For example, a stored procedure may select rows from one table, iterate through the result set and, based on the values in each row, insert, update or delete rows in other tables. A client program could do this as well, but a stored procedure is generally more efficient because queries and result sets don't have to be sent back and forth between the client and database. Also, stored procedures are generally stored in the database in a compiled state, while queries may have to be re-parsed and re-compiled each time they are sent.

While many databases support stored procedures. The syntax for creating and executing stored procedures varies greatly between databases.

Stored procedures typically take input paramters from client programs through input bind variables and return values back to client programs either through bind variables or result sets. Stored procedures can be broken down into several categories, based on the values that they return. Some stored procedures don't return any values, some return a single value, some return multiple values and some return entire result sets.

### No Values

Some stored procedures don't return any values. Below are examples, illustrating how to create, execute and drop this kind of stored procedure for each database that SQL Relay supports.

#### Oracle

To create the stored procedure, run a query like the following.

>     create procedure exampleproc(in1 in number, in2 in number, in3 in varchar2) is
>     begin
>             insert into mytable values (in1,in2,in3);
>     end;

To execute the stored procedure from an SQL Relay program, use code like the following.

>     sqlrcur_prepareQuery(cur,"begin exampleproc(:in1,:in2,:in3); end;");
>     sqlrcur_inputBindLong(cur,"in1",1);
>     sqlrcur_inputBindDouble(cur,"in2",1.1,2,1);
>     sqlrcur_inputBindString(cur,"in3","hello");
>     sqlrcur_executeQuery(cur);

To drop the stored procedure, run a query like the following.

>     drop procedure exampleproc

#### Sybase and Microsoft SQL Server

To create the stored procedure, run a query like the following.

>     create procedure exampleproc @in1 int, @in2 float, @in3 varchar(20) as
>             insert into mytable values (@in1,@in2,@in3)

To execute the stored procedure from an SQL Relay program, use code like the following.

>     sqlrcur_prepareQuery(cur,"exec exampleproc");
>     sqlrcur_inputBindLong(cur,"in1",1);
>     sqlrcur_inputBindDouble(cur,"in2",1.1,2,1);
>     sqlrcur_inputBindString(cur,"in3","hello");
>     sqlrcur_executeQuery(cur);

To drop the stored procedure, run a query like the following.

>     drop procedure exampleproc

#### Firebird

To create the stored procedure, run a query like the following.

>     create procedure exampleproc(in1 integer, in2 float, in3 varchar(20)) as
>     begin
>             insert into mytable values (in1,in2,in3);
>             suspend;
>     end;

To execute the stored procedure from an SQL Relay program, use code like the following.

>     sqlrcur_prepareQuery(cur,"execute procedure exampleproc ?, ?, ?");
>     sqlrcur_inputBindLong(cur,"1",1);
>     sqlrcur_inputBindDouble(cur,"2",1.1,2,1);
>     sqlrcur_inputBindString(cur,"3","hello");
>     sqlrcur_executeQuery(cur);

To drop the stored procedure, run a query like the following.

>     drop procedure exampleproc

#### DB2

To create the stored procedure, run a query like the following.

>     create procedure exampleproc(in in1 int, in in2 double, in in3 varchar(20)) language sql
>     begin
>             insert into mytable values (in1,in2,in3);
>     end;

To execute the stored procedure from an SQL Relay program, use code like the following.

>     sqlrcur_prepareQuery(cur,"call exampleproc(?,?,?)");
>     sqlrcur_inputBindLong(cur,"1",1);
>     sqlrcur_inputBindDouble(cur,"2",1.1,2,1);
>     sqlrcur_inputBindString(cur,"3","hello");
>     sqlrcur_executeQuery(cur);

To drop the stored procedure, run a query like the following.

>     drop procedure exampleproc

#### Postgresql

To create the stored procedure, run a query like the following.

>     create function examplefunc(int,float,varchar(20)) returns void as '
>     begin
>             insert into mytable values ($1,$2,$3);
>             return;
>     end;' language plpgsql

To execute the stored procedure from an SQL Relay program, use code like the following.

>     sqlrcur_prepareQuery(cur,"select examplefunc($1,$2,$3)");
>     sqlrcur_inputBindLong(cur,"1",1);
>     sqlrcur_inputBindDouble(cur,"2",1.1,2,1);
>     sqlrcur_inputBindString(cur,"3","hello");
>     sqlrcur_executeQuery(cur);

To drop the stored procedure, run a query like the following.

>     drop function examplefunc(int,float,varchar(20))

#### MySQL/MariaDB

To create the stored procedure, run a query like the following.

>     create procedure exampleproc(in in1 int, in in2 float, in in3 varchar(20))
>     begin
>             insert into mytable values (in1,in2,in3);
>     end;

To execute the stored procedure from an SQL Relay program, use code like the following.

>     sqlrcur_prepareQuery(cur,"call exampleproc(?,?,?)");
>     sqlrcur_inputBindLong(cur,"1",1);
>     sqlrcur_inputBindDouble(cur,"2",1.1,2,1);
>     sqlrcur_inputBindString(cur,"3","hello");
>     sqlrcur_executeQuery(cur);

Note: Versions of MySQL prior to 5.0 had trouble calling stored procedures using bind variables. If you are using a version of MySQL prior to 5.0 then SQL relay must fake the bind variables and you must use colon-delimited variables (:1, :2, :3, etc.) in your queries rather than the native-mysql queston marks.

To drop the stored procedure, run a query like the following.

>     drop procedure exampleproc

### Single Values

Some stored procedures return single values. Below are examples, illustrating how to create, execute and drop this kind of stored procedure for each database that SQL Relay supports.

#### Oracle

In Oracle, stored procedures can return values through output parameters or as return values of the procedure itself.

Here is an example where the procedure itself returns a value. Note that Oracle calls these functions.

To create the stored procedure, run a query like the following.

>     create function exampleproc(in1 in number, in2 in number, in3 in varchar2) returns number is
>     begin
>             return in1;
>     end;

To execute the stored procedure from an SQL Relay program, use code like the following.

>     sqlrcur_prepareQuery(cur,"select exampleproc(:in1,:in2,:in3) from dual");
>     sqlrcur_inputBindLong(cur,"in1",1);
>     sqlrcur_inputBindDouble(cur,"in2",1.1,2,1);
>     sqlrcur_inputBindString(cur,"in3","hello");
>     sqlrcur_executeQuery(cur);
>     char    *result=sqlrcur_getFieldByIndex(cur,0,0);

To drop the stored procedure, run a query like the following.

>     drop procedure exampleproc

Here is an example where the value is returned through an output parameter.

To create the stored procedure, run a query like the following.

>     create procedure exampleproc(in1 in number, in2 in number, in3 in varchar2, out1 out number) as
>     begin
>             out1:=in1;
>     end;

To execute the stored procedure from an SQL Relay program, use code like the following.

>     sqlrcur_prepareQuery(cur,"begin exampleproc(:in1,:in2,:in3,:out1); end;");
>     sqlrcur_inputBindLong(cur,"in1",1);
>     sqlrcur_inputBindDouble(cur,"in2",1.1,2,1);
>     sqlrcur_inputBindString(cur,"in3","hello");
>     sqlrcur_defineOutputBindInteger(cur,"out1");
>     sqlrcur_executeQuery(cur);
>     int64_t    result=sqlrcur_getOutputBindInteger(cur,"out1");

To drop the stored procedure, run a query like the following.

>     drop procedure exampleproc

#### Sybase and Microsoft SQL Server

In Sybase and Microsoft SQL Server, stored procedures return values through output parameters rather than as return values of the procedure itself.

To create the stored procedure, run a query like the following.

>     create procedure exampleproc @in1 int, @in2 float, @in3 varchar(20), @out1 int output as
>             select @out1=convert(varchar(20),@in1)

To execute the stored procedure from an SQL Relay program, use code like the following.

>     sqlrcur_prepareQuery(cur,"exec exampleproc");
>     sqlrcur_inputBindLong(cur,"in1",1);
>     sqlrcur_inputBindDouble(cur,"in2",1.1,2,1);
>     sqlrcur_inputBindString(cur,"in3","hello");
>     sqlrcur_defineOutputBindInteger(cur,"out1");
>     sqlrcur_executeQuery(cur);
>     int64_t    result=sqlrcur_getOutputBindInteger(cur,"out1");

To drop the stored procedure, run a query like the following.

>     drop procedure exampleproc

#### Firebird

To create the stored procedure, run a query like the following.

>     create procedure exampleproc(in1 integer, in2 float, in3 varchar(20)) returns (out1 integer) as
>     begin
>             out1=in1;
>             suspend;
>     end;

To execute the stored procedure from an SQL Relay program, use code like the following.

>     sqlrcur_prepareQuery(cur,"select * from exampleproc(?,?,?)");
>     sqlrcur_inputBindLong(cur,"1",1);
>     sqlrcur_inputBindDouble(cur,"2",1.1,2,1);
>     sqlrcur_inputBindString(cur,"3","hello");
>     sqlrcur_executeQuery(cur);
>     char    *result=sqlrcur_getFieldByIndex(cur,0,0);

Alternatively, you can run a query like the following and receive the result using an output bind variable. Note that in Firebird, input and output bind variable indices are distict from one another. The index of the output bind variable is 1 rather than 4, even though there were 3 input bind variables.

>     sqlrcur_prepareQuery(cur,"execute procedure exampleproc ?, ?, ?");
>     sqlrcur_inputBindLong(cur,"1",1);
>     sqlrcur_inputBindDouble(cur,"2",1.1,2,1);
>     sqlrcur_inputBindString(cur,"3","hello");
>     sqlrcur_defineOutputBindInteger(cur,"1");
>     sqlrcur_executeQuery(cur);
>     int64_t    result=sqlrcur_getOutputBindInteger(cur,"1");

To drop the stored procedure, run a query like the following.

>     drop procedure exampleproc

#### DB2

In DB2, stored procedures return values through output parameters rather than as return values of the procedure itself.

To create the stored procedure, run a query like the following.

>     create procedure exampleproc(in in1 int, in in2 double, in in3 varchar(20), out out1 int) language sql
>     begin
>             set out1 = in1;
>     end

To execute the stored procedure from an SQL Relay program, use code like the following.

>     sqlrcur_prepareQuery(cur,"call exampleproc(?,?,?,?)");
>     sqlrcur_inputBindLong(cur,"1",1);
>     sqlrcur_inputBindDouble(cur,"2",1.1,2,1);
>     sqlrcur_inputBindString(cur,"3","hello");
>     sqlrcur_defineOutputBindInteger(cur,"4");
>     sqlrcur_executeQuery(cur);
>     int64_t    result=sqlrcur_getOutputBindInteger(cur,"4");

To drop the stored procedure, run a query like the following.

>     drop procedure exampleproc

#### Postgresql

To create the stored procedure, run a query like the following.

>     create function examplefunc(int,float,char(20)) returns int as '
>     declare
>             in1 int;
>             in2 float;
>             in3 char(20);
>     begin
>             in1:=$1;
>             return;
>     end;
>     ' language plpgsql

To execute the stored procedure from an SQL Relay program, use code like the following.

>     sqlrcur_prepareQuery(cur,"select * from examplefunc(1,2,3)");
>     sqlrcur_inputBindLong(cur,"1",1);
>     sqlrcur_inputBindDouble(cur,"2",1.1,4,2);
>     sqlrcur_inputBindString(cur,"3","hello");
>     sqlrcur_executeQuery(cur);
>     char    *result=sqlrcur_getFieldByIndex(cur,0,0);

To drop the stored procedure, run a query like the following.

>     drop function examplefunc(int,float,char(20))

#### MySQL/MariaDB

A single value can be returned from a MySQL/MariaDB function.

To create the function, run a query like the following.

>     create function examplefunc(in in1 int, in in2 float, in in3 varchar(20)) returns int return in1;

To execute the function from an SQL Relay program, use code like the following.

>     sqlrcur_prepareQuery(cur,"select examplefunc(?,?,?)");
>     sqlrcur_inputBindLong(cur,"1",1);
>     sqlrcur_inputBindDouble(cur,"2",1.1,4,2);
>     sqlrcur_inputBindString(cur,"3","hello");
>     sqlrcur_executeQuery(cur);
>     char    *result=sqlrcur_getFieldByIndex(cur,0,0);

Note: Versions of MySQL prior to 5.0 had trouble calling stored procedures using bind variables. If you are using a version of MySQL prior to 5.0 then SQL relay must fake the bind variables and you must use colon-delimited variables (:1, :2, :3, etc.) in your queries rather than the native-mysql queston marks.

To drop the function, run a query like the following.

>     drop procedure exampleproc

A single value can be returned in the result set of a MySQL/MariaDB procedure.

To create the procedure, run a query like the following.

>     create procedure exampleproc() begin select 1; end;

To execeute the procedure from an SQL Relay program, use code like the following.

>     sqlrcur_sendQuery(cur,"select exampleproc()");
>     char    *result=sqlrcur_getFieldByIndex(cur,0,0);

To drop the procedure, run a query like the following.

>     drop procedure exampleproc

A single value can be returned using the output variable of a MySQL/MariaDB procedure.

To create the procedure, run a query like the following.

>     create procedure exampleproc(out out1 int) begin select 1 into out1; end;

To execeute the procedure from an SQL Relay program, use code like the following.

>     sqlrcur_sendQuery(cur,"set @out1=0");
>     sqlrcur_sendQuery(cur,"call exampleproc(@out1)");
>     sqlrcur_sendQuery(cur,"select @out1");
>     char    *result=sqlrcur_getFieldByIndex(cur,0,0);

To drop the procedure, run a query like the following.

>     drop procedure exampleproc

### Multiple Values

Some stored procedures return multiple values. Below are examples, illustrating how to create, execute and drop this kind of stored procedure for each database that SQL Relay supports.

#### Oracle

In Oracle, stored procedures can return values through output parameters or as return values of the procedure itself. If a procedure needs to return multiple values, it can return one of them as the return value of the procedure itself, but the rest must be returned through output parameters.

To create the stored procedure, run a query like the following.

>     create procedure exampleproc(in1 in number, in2 in number, in3 in varchar2, out1 out number, out2 out number, out3 out varchar2) is
>     begin
>             out1:=in1;
>             out2:=in2;
>             out3:=in3;
>     end;

To execute the stored procedure from an SQL Relay program, use code like the following.

>     sqlrcur_prepareQuery(cur,"begin exampleproc(:in1,:in2,:in3,:out1,:out2,:out3); end;");
>     sqlrcur_inputBindLong(cur,"in1",1);
>     sqlrcur_inputBindDouble(cur,"in2",1.1,2,1);
>     sqlrcur_inputBindString(cur,"in3","hello");
>     sqlrcur_defineOutputBindInteger(cur,"out1");
>     sqlrcur_defineOutputBindDouble(cur,"out2");
>     sqlrcur_defineOutputBindString(cur,"out3",20);
>     sqlrcur_executeQuery(cur);
>     int64_t out1=sqlrcur_getOutputBindInteger(cur,"out1");
>     double  out2=sqlrcur_getOutputBindDouble(cur,"out2");
>     char    *out3=sqlrcur_getOutputBindString(cur,"out3");

To drop the stored procedure, run a query like the following.

>     drop procedure exampleproc

#### Sybase and Microsoft SQL Server

To create the stored procedure, run a query like the following.

>     create procedure exampleproc @in1 int, @in2 float, @in3 varchar(20), @out1 int output, @out2 int output, @out3 int output as
>             select @out1=convert(varchar(20),@in1),
>                     @out2=convert(varchar(20),@in2),
>                     @out2=convert(varchar(20),@in2)

To execute the stored procedure from an SQL Relay program, use code like the following.

>     sqlrcur_prepareQuery(cur,"exec exampleproc");
>     sqlrcur_inputBindLong(cur,"in1",1);
>     sqlrcur_inputBindDouble(cur,"in2",1.1,2,1);
>     sqlrcur_inputBindString(cur,"in3","hello");
>     sqlrcur_defineOutputBindInteger(cur,"out1");
>     sqlrcur_defineOutputBindDouble(cur,"out2");
>     sqlrcur_defineOutputBindString(cur,"out3",20);
>     sqlrcur_executeQuery(cur);
>     int64_t out1=sqlrcur_getOutputBindInteger(cur,"out1");
>     double  out2=sqlrcur_getOutputBindDouble(cur,"out2");
>     char    *out3=sqlrcur_getOutputBindString(cur,"out3");

To drop the stored procedure, run a query like the following.

>     drop procedure exampleproc

#### Firebird

To create the stored procedure, run a query like the following.

>     create procedure exampleproc(in1 integer, in2 float, in3 varchar(20)) returns (out1 integer, out2 float, out3 varchar(20)) as
>     begin
>             out1=in1;
>             out2=in2;
>             out3=in3;
>             suspend;
>     end;

To execute the stored procedure from an SQL Relay program, use code like the following.

>     sqlrcur_prepareQuery(cur,"select * from exampleproc(?,?,?)");
>     sqlrcur_inputBindLong(cur,"1",1);
>     sqlrcur_inputBindDouble(cur,"2",1.1,2,1);
>     sqlrcur_inputBindString(cur,"3","hello");
>     sqlrcur_executeQuery(cur);
>     char    *out1=sqlrcur_getFieldByIndex(cur,0,0);
>     char    *out2=sqlrcur_getFieldByIndex(cur,0,1);
>     char    *out3=sqlrcur_getFieldByIndex(cur,0,2);

Alternatively, you can run a query like the following and receive the result using a output bind variables. Note that in Firebird, input and output bind variable indices are distict from one another. The index of the first output bind variable is 1 rather than 4, even though there were 3 input bind variables.

>     sqlrcur_prepareQuery(cur,"execute procedure exampleproc ?, ?, ?");
>     sqlrcur_inputBindLong(cur,"1",1);
>     sqlrcur_inputBindDouble(cur,"2",1.1,2,1);
>     sqlrcur_inputBindString(cur,"3","hello");
>     sqlrcur_defineOutputBindInteger(cur,"1");
>     sqlrcur_defineOutputBindDouble(cur,"2");
>     sqlrcur_defineOutputBindString(cur,"3",20);
>     sqlrcur_executeQuery(cur);
>     int64_t out1=sqlrcur_getOutputBindInteger(cur,"1");
>     double  out2=sqlrcur_getOutputBindDouble(cur,"2");
>     char    *out3=sqlrcur_getOutputBindString(cur,"3");

To drop the stored procedure, run a query like the following.

>     drop procedure exampleproc

#### DB2

To create the stored procedure, run a query like the following.

>     create procedure exampleproc(in in1 int, in in2 double, in in3 varchar(20), out out1 int, out out2 double, out out3 varchar(20)) language sql
>     begin
>             set out1 = in1;
>             set out2 = in2;
>             set out3 = in3;
>     end

To execute the stored procedure from an SQL Relay program, use code like the following.

>     sqlrcur_prepareQuery(cur,"call exampleproc(?,?,?,?,?,?)");
>     sqlrcur_inputBindLong(cur,"1",1);
>     sqlrcur_inputBindDouble(cur,"2",1.1,2,1);
>     sqlrcur_inputBindString(cur,"3","hello");
>     sqlrcur_defineOutputBindInteger(cur,"4");
>     sqlrcur_defineOutputBindDouble(cur,"5");
>     sqlrcur_defineOutputBindString-(cur,"6",25);
>     sqlrcur_executeQuery(cur);
>     int64_t out1=sqlrcur_getOutputBindInteger(cur,"4");
>     double  out2=sqlrcur_getOutputBindDouble(cur,"5");
>     char    *out3=sqlrcur_getOutputBindString(cur,"6");

To drop the stored procedure, run a query like the following.

>     drop procedure exampleproc

#### Postgresql

To create the stored procedure, run a query like the following.

>     create function examplefunc(int,float,char(20)) returns record as '
>     declare
>             output record;
>     begin
>             select $1,$2,$3 into output;
>             return output;
>     end;
>     ' language plpgsql

To execute the stored procedure from an SQL Relay program, use code like the following.

>     sqlrcur_prepareQuery(cur,"select * from examplefunc(1,2,3) as (col1 int, col2 float, col3 char(20))");
>     sqlrcur_inputBindLong(cur,"1",1);
>     sqlrcur_inputBindDouble(cur,"2",1.1,4,2);
>     sqlrcur_inputBindString(cur,"3","hello");
>     sqlrcur_executeQuery(cur);
>     char    *out1=sqlrcur_getFieldByIndex(cur,0,0);
>     char    *out2=sqlrcur_getFieldByIndex(cur,0,1);
>     char    *out3=sqlrcur_getFieldByIndex(cur,0,2);

To drop the stored procedure, run a query like the following.

>     drop function examplefunc(int,float,char(20))

#### MySQL/MariaDB

Here's how you can get multiple values from the result set of a MySQL/MariaDB procedure.

To create the stored procedure, run a query like the following.

>     create procedure exampleproc(in in1 int, in in2 float, in in3 varchar(20)) begin select in1, in2, in3; end;

To execute the stored procedure from an SQL Relay program, use code like the following.

>     sqlrcur_prepareQuery(cur,"call exampleproc(?,?,?)");
>     sqlrcur_inputBindLong(cur,"1",1);
>     sqlrcur_inputBindDouble(cur,"2",1.1,4,2);
>     sqlrcur_inputBindString(cur,"3","hello");
>     sqlrcur_executeQuery(cur);
>     char    *out1=sqlrcur_getFieldByIndex(cur,0,0);
>     char    *out2=sqlrcur_getFieldByIndex(cur,0,1);
>     char    *out3=sqlrcur_getFieldByIndex(cur,0,2);

Note: Versions of MySQL prior to 5.0 had trouble calling stored procedures using bind variables. If you are using a version of MySQL prior to 5.0 then SQL relay must fake the bind variables and you must use colon-delimited variables (:1, :2, :3, etc.) in your queries rather than the native-mysql queston marks.

To drop the stored procedure, run a query like the following.

>     drop procedure exampleproc

Here's how you can get multiple values from the output variables of a MySQL/MariaDB procedure.

To create the stored procedure, run a query like the following.

>     create procedure exampleproc(out out1 int, out out2 float, out out3 varchar(20)) begin select 1,1.1,'hello' into out1, out2, out3; end;

To execute the stored procedure from an SQL Relay program, use code like the following.

>     sqlrcur_sendQuery(cur,"set @out1=0, @out2=0.0, @out3=''");
>     sqlrcur_sendQuery(cur,"call exampleproc(@out1,@out3,@out3)");
>     sqlrcur_sendQuery(cur,"select @out1,@out2,@out3");
>     char    *out1=sqlrcur_getFieldByIndex(cur,0,0);
>     char    *out2=sqlrcur_getFieldByIndex(cur,0,1);
>     char    *out3=sqlrcur_getFieldByIndex(cur,0,2);

To drop the stored procedure, run a query like the following.

>     drop procedure exampleproc

### Result Sets

Some stored procedures return entire result sets. Below are examples, illustrating how to create, execute and drop this kind of stored procedure for each database that SQL Relay supports.

#### Oracle

To create the stored procedure, run a query like the following.

>     create or replace package types as
>             type cursorType is ref cursor;
>     end;

>     create function exampleproc return types.cursortype is
>             l_cursor    types.cursorType;
>     begin
>             open l_cursor for select * from mytable;
>             return l_cursor;
>     end;

To execute the stored procedure from an SQL Relay program, use code like the following.

>     sqlrcur_prepareQuery(cur,"begin  :curs:=exampleproc; end;");
>     sqlrcur_defineOutputBindCursor(cur,"curs");
>     sqlrcur_executeQuery(cur);
>     sqlrcur bindcur=sqlrcur_getOutputBindCursor(cur,"curs");
>     sqlrcur_fetchFromBindCursor(bindcur);
>     char    *field00=sqlrcur_getFieldByIndex(bindcur,0,0);
>     char    *field01=sqlrcur_getFieldByIndex(bindcur,0,1);
>     char    *field02=sqlrcur_getFieldByIndex(bindcur,0,2);
>     char    *field10=sqlrcur_getFieldByIndex(bindcur,1,0);
>     char    *field11=sqlrcur_getFieldByIndex(bindcur,1,1);
>     char    *field12=sqlrcur_getFieldByIndex(bindcur,1,2);

To drop the stored procedure, run a query like the following.

>     drop function exampleproc
>     drop package types

#### Sybase and Microsoft SQL Server

To create the stored procedure, run a query like the following.

>     create procedure exampleproc as select * from exampletable

To exceute the stored procedure from an SQL Relay program, ue code like the following.

>     sqlrcur_sendQuery(cur,"exec exampleproc");
>     char    *field00=sqlrcur_getFieldByIndex(cur,0,0);
>     char    *field01=sqlrcur_getFieldByIndex(cur,0,1);
>     char    *field02=sqlrcur_getFieldByIndex(cur,0,2);
>     char    *field10=sqlrcur_getFieldByIndex(cur,1,0);
>     char    *field11=sqlrcur_getFieldByIndex(cur,1,1);
>     char    *field12=sqlrcur_getFieldByIndex(cur,1,2);

To drop the stored procedure, run a query like the following.

>     drop procedure exampleproc

#### Firebird

Stored procedures in Firebird can return a result set if a select query in the procedure selects values into the output parameters and then issues a suspend command, however SQL Relay doesn't currently support stored procedures that return result sets.

#### DB2

Stored procedures in DB2 can return a result set if the procedure is declared to return one, however SQL Relay doesn't currently support stored procedures that return result sets.

#### Postgresql

To create the stored procedure, run a query like the following.

>     create function examplefunc() returns setof record as '
>             declare output record;
>     begin
>             for output in select * from mytable loop
>                     return next output;
>             end loop;
>             return;
>     end;
>     ' language plpgsql

To execute the stored procedure from an SQL Relay program, use code like the following.

>     sqlrcur_sendQuery(cur,"select * from examplefunc() as (exampleint int, examplefloat float, examplechar char(40))");
>     char    *field00=sqlrcur_getFieldByIndex(cur,0,0);
>     char    *field01=sqlrcur_getFieldByIndex(cur,0,1);
>     char    *field02=sqlrcur_getFieldByIndex(cur,0,2);
>     char    *field10=sqlrcur_getFieldByIndex(cur,1,0);
>     char    *field11=sqlrcur_getFieldByIndex(cur,1,1);
>     char    *field12=sqlrcur_getFieldByIndex(cur,1,2);

To drop the stored procedure, run a query like the following.

>     drop function examplefunc

#### MySQL/MariaDB

The result sets of all select statements called within MySQL/MariaDB stored procedures (that aren't selected into variables) are returned from the procedure call. Though MySQL/MariaDB stored procedures can return multiple result sets, currently SQL Relay can only fetch the first result set.

To create the stored procedure which returns a result set, run a query like the following.

>     create procedure exampleproc() begin select * from mytable; end;

To execute the stored procedure from an SQL Relay program, use code like the following.

>     sqlrcur_sendQuery(cur,"call exampleproc()");
>     char    *field00=sqlrcur_getFieldByIndex(cur,0,0);
>     char    *field01=sqlrcur_getFieldByIndex(cur,0,1);
>     char    *field02=sqlrcur_getFieldByIndex(cur,0,2);
>     char    *field10=sqlrcur_getFieldByIndex(cur,1,0);
>     char    *field11=sqlrcur_getFieldByIndex(cur,1,1);
>     char    *field12=sqlrcur_getFieldByIndex(cur,1,2);

To drop the stored procedure, run a query like the following.

>     drop procedure exampleproc

## Caching The Result Set

Say you're writing a web-based report where a query with a huge result set is executed and 20 rows are displayed per page. Rather than rerunning the query for every page every time and dumping all but the 20 rows you want to display, you can run the query once, cache the result set to a local file and just open the file for each page of the report.

First page:

>     #include <sqlrelay/sqlrclientwrapper.h>
>     #include <stdio.h>

>     main() {

>             char       *filename;

>             sqlrcon      con=sqlrcon_alloc("sqlrserver",9000,"/tmp/example.socket","user","password",0,1);
>             sqlrcur      cur=sqlrcur_alloc(con);

>     	... generate a unique file name ...

>             sqlrcur_cacheToFile(cur,filename);
>             sqlrcur_setCacheTtl(cur,600);
>             sqlrcur_sendQuery(cur,"select * from my_table");
>             sqlrcon_endSession(con);
>             sqlrcur_cacheOff(cur);

>             ... pass the filename to the next page ...

>             sqlrcur_free(cur);
>             sqlrcon_free(con);
>     }

Second page:

>     #include <sqlrelay/sqlrclientwrapper.h>
>     #include <stdio.h>

>     main() {

>             int        row,col;

>             ... get the filename from the previous page ...

>             ... get the page to display from the previous page ...

>             sqlrcon      con=sqlrcon_alloc("sqlrserver",9000,"/tmp/example.socket","user","password",0,1);
>             sqlrcur      cur=sqlrcur_alloc(con);

>             sqlrcur_openCachedResultSet(cur,filename);
>             sqlrcon_endSession(con);

>             for (row=pagetodisplay*20; row<(pagetodisplay+1)*20; row++) {
>                     for (col=0; col<sqlrcur_colCount(cur); col++) {
>                             printf("%s,",sqlrcur_getFieldByIndex(cur,row,col));
>                     }
>                     printf("\n");
>             }

>             sqlrcur_free(cur);
>             sqlrcon_free(con);
>     }

For result-set caching to be effective, the sqlr-cachemanager process must be enabled and running on the client system. The sqlr-cachemanager scans the cache periodically and deletes cached result sets whos ttl's have expired. If it is not running, stale result sets persist beyond their intended ttl's.

To enable the sqlr-cachemanager at boot on systemd platforms:

>     systemctl enable sqlrcachemanager.service

To start the sqlr-cachemanager on systemd platforms:

>     systemctl start sqlrcachemanager.service

To enable the sqlr-cachemanager at boot on most non-systemd platforms, you must create a symlink into the /etc/rc2.d or /etc/rc3.d directory. Eg:

>     cd /etc/rc2.d
>     ln -s ../init.d/sqlrcachemanager S15sqlrcachemanager

> or

>     cd /etc/rc3.d
>     ln -s ../init.d/sqlrcachemanager S15sqlrcachemanager

To start the sqlr-cachemanager on most non-systemd platforms:

>     /etc/init.d/sqlrcachemanager start

To enable the sqlr-cachemanager at boot on FreeBSD platforms, edit /etc/rc.conf and add a line like:

>     sqlrcachemanager_enable=YES

To enable the sqlr-cachemanager at boot on NetBSD platforms, edit /etc/rc.conf and add a line like:

>     sqlrcachemanager=YES

To enable the sqlr-cachemanager at boot on OpenBSD platforms, edit /etc/rc.conf and add a line like:

>     sqlrcachemanager_flags=YES

To start the sqlr-cachemanager on BSD platforms:

>     /etc/init.d/sqlrcachemanager start

## Suspending and Resuming Sessions

Sometimes web-based applications need a single database transaction to span multiple pages. Since SQL Relay sessions can be suspended and resumed, this is possible.

First page:

>     #include <sqlrelay/sqlrclientwrapper.h>
>     #include <stdio.h>

>     main() {

>             int        port;
>             char       *socket;
>             int        rs;

>             sqlrcon      con=sqlrcon_alloc("sqlrserver",9000,"/tmp/example.socket","user","password",0,1);
>             sqlrcur      cur=sqlrcur_alloc(con);

>             sqlrcur_sendQuery(cur,"insert into my_table values (1,2,3)");
>     	sqlrcur_suspendResultSet(cur);
>             sqlrcon_suspendSession(con);
>     	rs=sqlrcur_getResultSetId(cur);
>             port=getConnectionPort(cur);
>             socket=getConnectionSocket(cur);

>             ... pass the rs, port and socket to the next page ...

>             sqlrcur_free(cur);
>             sqlrcon_free(con);
>     }

Second page:

>     #include <sqlrelay/sqlrclientwrapper.h>
>     #include <stdio.h>

>     main() {

>             ... get rs, port and socket from previous page ...

>             sqlrcon      con=sqlrcon_alloc("sqlrserver",9000,"/tmp/example.socket","user","password",0,1);
>             sqlrcur      cur=sqlrcur_alloc(con);

>             sqlrcon_resumeSession(con,port,socket);
>     	sqlrcur_resumeResultSet(cur,rs);
>             sqlrcur_sendQuery(cur,"commit");
>             sqlrcon_endSession(con);

>             sqlrcur_free(cur);
>             sqlrcon_free(con);
>     }

You can also distribute the processing of a result set across a series of pages using suspended sessions. If you're buffering a result set in chunks instead of all at once and suspend a session, when you resume the session you can continue to retrieve rows from the result set.

Similarly, if you're buffering a result set in chunks, caching that result set and suspend your session. When you resume the session, you can continue caching the result set. You must use sqlrcur_resumeCachedResultSet() instead of sqlrcur_resumeResultSet() however.

## Getting the Last Insert ID

Databases with autoincrement or identity columns often provide functions which return the "last insert id"; the value of the autoincrement column that was generated during the insert into the database.

SQL Relay provides the sqlrcon_getLastInsertId() function to get this value.

When using the SQLite database, you can also get the last insert id by running the query:

> select last insert rowid