Describing the Statement Type
This statement takes a statement identifier from a PREPARE statement as input. After DESCRIBE INPUT executes, the SQLCODE field of the sqlca indicates the statement type (that is, the keyword with which the statement begins). If a prepared object contains more than one SQL statement, DESCRIBE INPUT returns the type of the first statement in the prepared text.
SQLCODE is set to zero to indicate a SELECT statement without an INTO TEMP clause. This situation is the most common. For any other SQL statement, SQLCODE is set to a positive integer. You can compare the number with the named constants that are defined in the sqlstypes.h header file.
The DESCRIBE and DESCRIBE INPUT statements use SQLCODE differently from other statements, under some circumstances returning a nonzero value after successful execution. You can revise standard error-checking routines to accommodate this behavior, if desired.