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CREATE TRIGGER trigger_name trigger_time trigger_event
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| bet | 3/4 | | Sana | 03.12.2023 | | Hajmi | 117,21 Kb. | | #110281 |
CREATE TRIGGER trigger_name trigger_time trigger_event ON tbl_name FOR EACH ROW trigger_stmt* Ushbu kod manba kodi bilan ta'kidlangan
trigger_name — trigerni nomi
trigger_time — trigerni ishlaash vaqti BEFORE — Bajarishdan oldin. AFTER — bajarishdan keyin.
trigger_event — Hodisa:
insert — Hodisa insert, data load, replace operatorlar bilan amalga oshadi.
update — Hodisa update operatori bilan amalga oshadi.
delete — Hodisa delete, replace operatorlar bilan amalga oshaditbl_name — jadval nomi.
trigger_stmt trigger aktivlashganda bajariladigan ifoda
Quyidagi hodisalar uchun triggerlar yaratish mumkin:
BEFORE INSERT va AFTER INSERT…
BEFORE UPDATE va AFTER UPDATE
BEFORE DELETE va AFTER DELETE…
| Qo’llanilishi
CREATE TABLE Hisob (H_id INT, Middori DECIMAL(10,2)); CREATE TRIGGER summa BEFORE INSERT ON hisob FOR EACH ROW SET @sum = @sum + NEW.Middori;
O'zgaruvchidan oldingi @ belgisi global o'zgaruvchini anglatadi. Uning mysql serveri triggerdan chiqqandan keyin eslab qoladi va uni keyinchalik, masalan, bu kabi ham chaqirish mumkin. select @sum;
New degani biz eski qiymatni emas, balki yangi qiymatni olishimizni anglatadi (OLD eskisi uchun ishlatiladi).
FOR EACH ROW- bu siklga o'xshash narsa, ya'ni trigger biriktirilgan jadvalning har bir qatori uchun keyingi nuqta-vergulga o'tiladi. mysql> set @sum=0; Query OK, 0 rows affected (0.08 sec)
mysql> INSERT INTO hisob VALUES(137,14.98),(141,1937.50),(97,-100.00); Query OK, 3 rows affected (0.29 sec) Records: 3 Duplicates: 0 Warnings: 0
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