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Implicit Status Checking
You can use the WHENEVER command, as at 6 in Figure 3-1, to have
ALLBASE/SQL examine SQLCA values and cause a specific action to be taken.
The WHENEVER command is a preprocessor directive that specifies the
action to be taken for each subsequent SQL command, if an error or
warning condition occurs during execution of the SQL command.
EXEC SQL WHENEVER SQLERROR GOTO 500
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the condition
Preprocessor-generated statements for each WHENEVER command are embedded
into the preprocessed code after each subsequent SQL command found in the
program's source code. Because of this, you must either end each program
unit which contains a WHENEVER condition GOTO label statement with a
WHENEVER condition CONTINUE statement, or have a label in each subsequent
program unit in the preprocessed source code which corresponds to the
appropriate WHENEVER condition GOTO label statement. If no label exists
and a WHENEVER condition CONTINUE statement is not entered, an error will
occur at compile time.
For example, if execution of the SELECT command at 8 or the SQLEXPLAIN
command at 10, illustrated earlier in this chapter, were to cause an
error condition, ALLBASE/SQL would take no special action because the
WHENEVER command shown at 6 precedes both the SELECT and the SQLEXPLAIN
commands in the source listing.
If, however, the WHENEVER SQLERROR CONTINUE statement was not entered and
an error occurred at 8, there would be a compile time error as there is
no label 500 in Subroutine QueryTable. The WHENEVER SQLERROR CONTINUE
command at 6 turns off the implicit status checking of the command that
appears earlier in the source listing:
EXEC SQL WHENEVER SQLERROR GOTO 500
This WHENEVER command specifies where to pass control when an error
occurs during execution of the CONNECT, BEGIN WORK, COMMIT WORK, or
COMMIT WORK RELEASE commands.
Although you can use a WHENEVER command to have ALLBASE/SQL examine the
values in certain fields of the SQLCA, you can also examine the values
yourself, as discussed under "Explicit Status Checking" later in this
chapter.