Trigger not ending execution or input - sql

Question

I have to check before inserting or updating a certain relation whether a particular row attribute in relation A is equal or greater than a corresponding row attribute in relation B. I wrote a trigger:
Attempt:
CREATE TRIGGER CandyCons AFTER INSERT, UPDATE ON Rel_A
AS
IF EXISTS (
SELECT * FROM Rel_A A, Rel_B B WHERE A.ID = B.ID AND A.candy > B.too_much
)
BEGIN
RAISERROR ('Stop eating!', 16, 1);
ROLLBACK TRANSACTION;
RETURN;
END;
I can't execute this. When I run it, I start getting line numbers like:
query
12
13
14
15
......... and so on
What should I do?

Answer 1

This can be done with a row level TRIGGER as in the following example.
First create the tables:
CREATE TABLE REL_B(ID NUMBER NOT NULL PRIMARY KEY, TOO_MUCH NUMBER);
CREATE TABLE REL_A(ID NUMBER NOT NULL REFERENCES REL_B(ID), CANDY NUMBER);
Then add some test data:
INSERT INTO REL_B VALUES (1,10);
INSERT INTO REL_B VALUES (2,20);
COMMIT;
Then create your TRIGGER:
CREATE OR REPLACE TRIGGER CANDYCONS
AFTER INSERT OR UPDATE ON REL_A
FOR EACH ROW
DECLARE
V_COUNT_TOO_MUCH_CANDY NUMBER := 0;
BEGIN
SELECT COUNT(*) INTO V_COUNT_TOO_MUCH_CANDY
FROM REL_B
WHERE REL_B.ID = :NEW.ID
AND :NEW.CANDY > REL_B.TOO_MUCH;
IF (V_COUNT_TOO_MUCH_CANDY > 0)
THEN
RAISE_APPLICATION_ERROR(-20144,'Stop eating!');
END IF;
END;
/
Then test:
These are ok:
INSERT INTO REL_A VALUES (1,9);
INSERT INTO REL_A VALUES (1,10);
But this is blocked:
INSERT INTO REL_A VALUES (1,11);
Error starting at line : 1 in command -
INSERT INTO REL_A VALUES (1,11)
Error report -
ORA-20144: Stop eating!

Answer 2

On the line after END;, enter a single slash (/) to tell SQLPlus to execute the current command buffer.
See also When do I need to use a semicolon vs a slash in Oracle SQL?
(There may be other issues with your code, and the other answers may address them. But I believe this is your immediate problem in terms of actually telling SQLPlus to compile and create the trigger.)

Answer 3

I believe you intend this:
CREATE TRIGGER CandyCons ON Rel_A
BEFORE INSERT, UPDATE
AS
IF EXISTS (SELECT 1 FROM Rel_B B WHERE :NEW.ID = B.ID AND :NEW.candy > B.too_much
)
BEGIN
RAISERROR ('Stop eating!', 16, 1);
ROLLBACK TRANSACTION;
RETURN;
END;
Wait. Oracle doesn't support if exists. And it requires then. So:
CREATE TRIGGER CandyCons ON Rel_A BEFORE INSERT, UPDATE
DECLARE
v_cnt number;
BEGIN
SELECT COUNT(*) INTO v_cnt
FROM Rebl_B B
WHERE :NEW.ID = B.ID AND :NEW.candy > B.too_much;
IF v_cnt = 0 THEN
BEGIN
RAISERROR ('Stop eating!', 16, 1);
ROLLBACK TRANSACTION;
RETURN;
END;
END;