mysql Error1093错误
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场景演示: mysql> create table test(id int,name varchar(12),primary key(id)); Query OK, 0 rows affected (0.04 sec) mysql> insert into test values(1,‘ttt‘); Query OK, 1 row affected (0.00 sec) mysql> insert into test values(2,‘ttt‘); Query OK, 1 row affected (0.00 sec) mysql> commit; Query OK, 0 rows affected (0.00 sec) mysql> update test set name=‘aaaa‘ where id in (select id from test); ERROR 1093 (HY000): You can‘t specify target table ‘test‘ for update in FROM clause
官方说明:
Error: 1093 SQLSTATE: HY000 (ER_UPDATE_TABLE_USED)
Message: You can‘t specify target table ‘%s‘ for update in FROM clause
This error occurs for attempts to select from and modify the same table within a single statement. If the select attempt occurs within a derived table, you can avoid this error by setting the derived_merge flag of the optimizer_switch system variable to force the subquery to be materialized into a temporary table, which effectively causes it to be a different table from the one modified. See Section 9.2.2.3, “Optimizing Derived Tables and View References”.
mysql不支持,在一条语句对同一个表,先查询再更新的操作。
解决方法1:改成sql
比如:利用临时表
mysql> update test set name=‘aaaa‘ where id in (select id from (select id from test)c); Query OK, 2 rows affected (0.02 sec) Rows matched: 2 Changed: 2 Warnings: 0
解决方法2:
官方说:可以通过设置optimizer_switch的 derived_merge参数来解决。
备注:Oracle是不会这个问题的
本文出自 “corasql” 博客,请务必保留此出处http://corasql.blog.51cto.com/5908329/1912236
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