Specifies the statement(s) the host language will perform if
an error occurs during the execution of the associated data
manipulation statement. The statements can be host language
statements or Oracle Rdb data manipulation statements.
NOTE
ON ERROR is supported only for the high-level language
preprocessors. ON ERROR is not supported for RDO or Callable
RDO.
1 – Format
(B)0[m[4mON[m [4mERROR[m qwq> statement qwq> [4mEND_ERROR[m
mqqqqqqqq<qqqqqj
statement
Any valid host language statement or Oracle Rdb data manipulation
statement. Separate multiple statements with the appropriate
delimiter or terminator according to the rules of the host
language.
2 – Example
This BASIC program uses LIB$MATCH_COND to handle errors that
occur in the MODIFY statement:
30
&RDB& START_TRANSACTION READ_WRITE
45 ! Input data
!
PRINT
INPUT "enter status code"; STATUS_CODE
PRINT
INPUT "enter status name"; STATUS_NAME
PRINT
INPUT "enter status type"; STATUS_TYPE
50 ! Modify the record
!
&RDB& FOR W IN WORK_STATUS
&RDB& MODIFY W USING
&RDB& ON ERROR
GOSUB 1000
&RDB& END_ERROR
&RDB& W.STATUS_CODE = STATUS_CODE;
&RDB& W.STATUS_NAME = STATUS_NAME;
&RDB& W.STATUS_TYPE = STATUS_TYPE
&RDB& END_MODIFY
PRINT
PRINT STATUS_CODE, STATUS_NAME, STATUS_TYPE
&RDB& END_FOR
GO TO 5000
1000 MATCH_COND = &
LIB$MATCH_COND(RDB$STATUS,RDB$_NOT_VALID)
SELECT MATCH_COND
CASE 1
PRINT "You have entered invalid data. Try again."
CALL SYS$PUTMSG(RDB$MESSAGE_VECTOR)
&RDB& ROLLBACK
GOTO 20
CASE 0
PRINT "Unknown error"
CALL SYS$PUTMSG(RDB$MESSAGE_VECTOR)
&RDB& ROLLBACK
GO TO 5000
END SELECT
RETURN
5000
&RDB& FINISH
END
This excerpt from a BASIC program performs the following actions:
o Prompts for input for the MODIFY statement.
o Starts a FOR loop.
o If an error occurs in the MODIFY statement, the program
branches to the call to LIB$MATCH_COND. This run-time library
procedure matches the condition value that Oracle Rdb returns
to the program (RDB$STATUS) with the condition code RDB$_NOT_
VALID. If the return status is RDB$_NOT_VALID, the program
prints the appropriate message and loops back to prompt again.
If some other error code is detected, "Unknown error" is
displayed and the program stops.
3 – More
If you have invoked a database, you have the necessary privileges
to use the ON_ERROR clause.