MySQL 错误 - 无法更新存储的 function/trigger 中的 table 'library_audit2'，因为它已被语句使用

Question

删除记录时出现错误。触发器哪里有问题。

Mysql代码-

MariaDB [practice2]> delimiter $$
MariaDB [practice2]> create trigger BeforeLibraryDelete1
    -> BEFORE DELETE
    -> ON library_audit2 FOR EACH ROW
    -> BEGIN
    -> declare id1 int;
    -> select library_id into id1 from library_audit2 where change_date=OLD.change_date;
    -> delete from library_2 where library_2.id=id1;
    -> END $$
Query OK, 0 rows affected (0.128 sec)

MariaDB [practice2]> delimiter ;


MariaDB [practice2]> Delete from library_audit2 where change_date='2017-04-07';

触发删除查询时，出现错误 -

ERROR 1442 (HY000): Can't update table 'library_audit2' in stored function/trigger because it is already used by statement which invoked this stored function/trigger

Answer 1

您有一个针对每一行触发的删除触发器。我真的不明白从源 table 中再次选择只是为了获取要删除的行的 id。此信息已在触发器级别可用，在伪列 old.id1.

中

这不是你想要的吗？

create trigger beforelibrarydelete1
before delete on library_audit2 
for each row
begin
    delete from library_2 where id = old.id;
end $$

阅读问题下的评论，您似乎正在尝试使用此触发器处理外键依赖项。如果您在 library2 中有引用 library_audit2 的子记录，那么您可以使用 on delete cascade 选项在从父 table 删除记录时自动删除它们。

create table library2 (
    ...
    foreign key (id)
        references library_audit2(id)
        on delete cascade
);

MySQL 错误 - 无法更新存储的 function/trigger 中的 table 'library_audit2'，因为它已被语句使用

MySQL error - Can't update table 'library_audit2' in stored function/trigger because it is already used by statement

mysql

sql

triggers

sql-delete