Triggers
Trigger, EK, TABLE, PAR, EK, EVENT, (BEFORE/AFTER, INSERT/UPDATE/DELETE) SE, ASSOCIATE, kiya, jaata hai — JAB, WOH, EVENT, HOTA, hai, trigger, ka, code, AUTOMATICALLY, RUN, hota hai.
NEW, aur, OLD, KEYWORDS, se, trigger, ke, ANDAR, ROW, ki, NEW/OLD, VALUES, ACCESS, ki, ja, sakti, HAIN — jaise, EK, AUDIT, LOG, mein, KYA, CHANGE, HUA, ye, RECORD, karne, ke, liye.
DELIMITER //
CREATE TRIGGER before_user_update
BEFORE UPDATE ON users
FOR EACH ROW
BEGIN
INSERT INTO audit_log (user_id, old_email, new_email, changed_at)
VALUES (OLD.id, OLD.email, NEW.email, NOW());
END //
DELIMITER ;- Trigger = event, (INSERT/UPDATE/DELETE) PAR, automatically, fire, hota, hai
- NEW/OLD, keywords, se, row, ki, values, access, ki, ja, sakti, hain
- Debug, karna, mushkil, ho, sakta, hai — "hidden" logic, hai
BEFORE, triggers, event, hone, se, PEHLE, RUN, HOTE, HAIN — data, ko, MODIFY, karne, ke, liye, useful, HAIN (jaise, NEW.value, ko, VALIDATE/CHANGE, karna). AFTER, triggers, event, ke, BAAD, RUN, HOTE, HAIN — LOGGING, ya, RELATED, table, updates, ke, liye, useful, HAIN.
CREATE TRIGGER before_insert_user
BEFORE INSERT ON users
FOR EACH ROW
SET NEW.email = LOWER(NEW.email);MySQL 5.7+, mein, EK, HI, TABLE, aur, EVENT, PAR, MULTIPLE, triggers, ho, sakte, HAIN — FOLLOWS/PRECEDES, keywords, se, execution, order, control, kiya, ja, sakta hai.