SQL/MX Programming Manual for C and COBOL (G06.24+, H06.03+)

Dynamic SQL With Descriptor Areas

HP NonStop SQL/MX Programming Manual for C and COBOL—523627-004

10-3

Allocating an SQL Descriptor Area

Use the ALLOCATE DESCRIPTOR statement to allocate a named SQL descriptor

area to store information necessary for the execution of dynamic SQL statements. If

needed, allocate two descriptor areas: one for input parameters and one for output

variables.

Use this general syntax:

For complete syntax, see the ALLOCATE DESCRIPTOR statement in the SQL/MX

Reference Manual.

The descriptor name is a literal or a host variable with a character data type that

specifies an SQL identifier at run time. The number of occurrences is specified to be a

host variable whose value is the maximum number of item descriptors, or the number

of parameters to be used in the dynamic SQL statements in your program.

Deallocating an SQL Descriptor Area

After the execution of dynamic SQL statements in your program, use the

DEALLOCATE DESCRIPTOR statement to deallocate an SQL descriptor area

previously allocated with ALLOCATE DESCRIPTOR.

Use this general syntax:

For complete syntax, see the DEALLOCATE DESCRIPTOR statement in the SQL/MX

Reference Manual.

The descriptor name for both the ALLOCATE DESCRIPTOR and DEALLOCATE

DESCRIPTOR statements includes specifying a GLOBAL or LOCAL scope. The scope

must be the same for these two statements using the same descriptor name within the

same module or compilation unit.

Input Parameters

An input parameter is a symbol in a dynamic SQL statement that serves as a

placeholder for a value substituted when the statement executes.

Specify input parameters in the statement as question marks (?), and use them in SQL

expressions wherever a constant is valid. Using a parameter, you can prepare an SQL

statement without the input values, which are substituted when the statement

executes. Specify the data type of the parameter explicitly by using the CAST function

so that NonStop SQL/MX correctly types the parameter.

ALLOCATE DESCRIPTOR descriptor-name WITH MAX occurrences

DEALLOCATE DESCRIPTOR descriptor-name