SQL descriptor area (SQLDA)

An SQLDA is a collection of variables that is required for execution of the SQL DESCRIBE statement, and can be optionally used by the PREPARE, OPEN, FETCH, EXECUTE, and CALL statements. An SQLDA can be used in a DESCRIBE or PREPARE INTO statement, modified with the addresses of host variables, and then reused in a FETCH statement.

The meaning of the information in an SQLDA depends on the context in which it is used. For DESCRIBE and PREPARE INTO, DB2® sets the fields in the SQLDA to provide information to the application program. For OPEN, EXECUTE, FETCH, and CALL, the application program sets the fields in the SQLDA to provide DB2 with information:

DESCRIBE statement-name or PREPARE INTO

With the exception of SQLN, DB2 sets fields of the SQLDA to provide information to an application program about a prepared statement. Each SQLVAR occurrence describes a column of the result table.

DESCRIBE TABLE

With the exception of SQLN, DB2 sets fields of the SQLDA to provide information to an application program about the columns of a table or view. Each SQLVAR occurrence describes a column of the specified table or view.

DESCRIBE CURSOR

With the exception of SQLN, DB2 sets fields of the SQLDA to provide information to an application program about the result set that is associated with the specified cursor. Each SQLVAR occurrence describes a column of the result set.

DESCRIBE INPUT

With the exception of SQLN, DB2 sets fields of the SQLDA to provide information to an application program about the input parameter markers of a prepared statement. Each SQLVAR occurrence describes an input parameter marker.

DESCRIBE PROCEDURE

With the exception of SQLN, DB2 sets fields of the SQLDA to provide information to an application program about the result sets returned by the specified stored procedure. Each SQLVAR occurrence describes a returned result set.

OPEN, EXECUTE, FETCH, and CALL

The application program sets fields of the SQLDA to provide information about host variables or output buffers in the application program to DB2. Each SQLVAR occurrence describes a host variable or output buffer.

For OPEN and EXECUTE, each SQLVAR occurrence describes an input value that is substituted for a parameter marker in the associated SQL statement that was previously prepared.
For FETCH, each SQLVAR occurrence describes a host variable or buffer in the application program that is to be used to contain an output value from a row of the result.
For CALL, each SQLVAR occurrence describes a host variable that corresponds to a parameter in the parameter list for the stored procedure.

For information on the way to use the SQLDA, see DB2 Application Programming and SQL Guide.

Description of SQLDA fields
An SQLDA consists of four variables, a header, and an arbitrary number of occurrences of a sequence of variables collectively named SQLVAR.
Unrecognized and unsupported SQLTYPES
The values that appear in the SQLTYPE field of the SQLDA are dependent on the level of data type support available at the sender as well as at the receiver of the data. This support is particularly important as new data types are added to the product.
The included SQLDA
Only assembler, C, C++, COBOL, and PL/I C are supported for the SQLDA that is given by INCLUDE SQLDA.
Identifying an SQLDA in C or C++
A descriptor-name can be specified in the CALL, DESCRIBE, EXECUTE, FETCH, and OPEN statements. When the host application is written in C or C++, descriptor-name can be a pointer variable with pointer notation.
The REXX SQLDA
A REXX SQLDA consists of a set of REXX variables with a common stem. The stem must be a REXX variable name that contains no periods and is the same as the value of descriptor-name that you specify when you use the SQLDA in an SQL statement. DB2 does not support the INCLUDE SQLDA statement in REXX.

Parent topic: Additional information for DB2 SQL