MySQL绕过错误1093

Question

错误1093表示如果子查询查询要删除的表,则无法使用子查询更新或删除.

所以你做不到

delete from table1 where id in (select something from table1 where condition) ;

好吧,解决这个限制的最佳方法是什么(假设您确实需要子查询来执行删除,并且不能完全消除自引用子查询？)

编辑:

以下是对有兴趣的人的查询:

mysql> desc adjacencies ;
+---------+---------+------+-----+---------+-------+
| Field   | Type    | Null | Key | Default | Extra |
+---------+---------+------+-----+---------+-------+
| parent  | int(11) | NO   | PRI | NULL    |       |
| child   | int(11) | NO   | PRI | NULL    |       |
| pathLen | int(11) | NO   |     | NULL    |       |
+---------+---------+------+-----+---------+-------+



-- The query is going to
-- tell all my children to
-- stop thinking my old parents
-- are still their parents

delete from adjacencies
where parent in 
(
-- ALL MY PARENTS,grandparents
  select parent
  from adjacencies
  where child=@me
  and parent!=@me
)

-- only concerns the relations of my
-- grandparents WHERE MY CHILDREN ARE CONCERNED
and child in
(
  -- get all my children
  select child
  from adjacencies
  where parent=@me
)

;

所以我到目前为止所尝试的是创建一个名为的临时表 adjsToDelete

create temporary table adjsToRemove( parent int, child int ) ;
insert into adjsToRemove...

所以现在我有一个要删除的关系集合,其中父/子对各自唯一地标识要删除的行.但是如何从邻接表中删除每一对呢？

看来我需要为auto_increment每个条目添加一个唯一的ed键adjacencies,是吗？

Answer 1

在http://bugs.mysql.com/bug.php?id=6980中找到的解决方法对我有用,就是为将返回项目的子查询创建一个别名.所以

delete from table1 where id in 
  (select something from table1 where condition)

会变成

delete from table1 where id in
  (select p.id from (select something from table1 where condition) as p)