Question

I am currently new in Firebird, especially in triggers. Usually, I do this in script manually, but I am really fascinated to create it with trigger.

Please let me explain my tables first.

***STOCK***
CODE
NAME
TOTAL
GOOD
BROKEN
SERVICE
***DETAIL***
ID
STOCK_CODE
SERIAL
***BROKEN***
DETAIL_ID
MARK
***SERVICE***
DETAIL_ID
START_DATE
END_DATE
COST
***LOGS***
DETAIL_ID
MARK
START_DATE
END_DATE
COST

And now my problems:

1. How to modify STOCK.GOOD and STOCK.BROKEN value after insert a new record into BROKEN? That will be: STOCK.GOOD-1, STOCK.BROKEN+1.

2. How to insert all record from BROKEN and SERVICE into LOGS before current record in SERVICE is deleted?

I hope my questions could be accepted.

Answer 1

Below are two triggers:

CREATE TRIGGER bi_broken FOR broken
  BEFORE INSERT
  POSITION 0
AS
BEGIN
  UPDATE stock SET good = good - 1, broken = broken + 1
    WHERE code = (SELECT d.stock_code 
      FROM detail d WHERE d.id = NEW.detail_id);
END


CREATE TRIGGER bd_service FOR service
  BEFORE DELETE
  POSITION 0
AS
BEGIN
  INSERT INTO logs (detail_id, mark, start_date, end_date, cost)
  SELECT detail_id, (SELECT b.mark FROM broken b WHERE b.detail_id = OLD.detail_id),
    start_date, end_date, cost
  FROM service 
  WHERE detail_id = OLD.detail_id;
END

By the way, what is a reason to put mark into a separate table? It belongs to STOCK, doesn’t it?