目的：當一張表中的數據達到一定條數時，讓其自動刪除本表固定條數的數據。代碼：--建表（就以student表為例）create table student(id int auto_increment primary key,name VARCHAR(20),age int)--觸發器CREATE TRIGGER tri_studentAFTER INSERT ON studentFOR EACH ROW BEGIN?? ?declare num INT;?? ?select count(id) INTO num from student;?? ?if num>=20 then ?? ??? ?DELETE FROM student WHERE ID>10;?? ?end if; ?END;--測試代碼insert into student(name,age) VALUES('aaa','22');--錯誤提示[SQL] insert into student(name,age) VALUES('aaa','22');[Err] 1442 - Can't update table 'student' in stored function/trigger because it is already used by statement which invoked this stored function/trigger.