MYSQL 更新与 WHERE SELECT 子查询错误

2022-01-23 00:00:00 select subquery mysql

我在获取选择子查询以处理 UPDATE 时遇到问题.我正在尝试以下方法:

I have an issue with getting select sub-queries to work on an UPDATE. I'm trying something like the following:

UPDATE foo
   SET bar=bar-1
 WHERE baz=
      (
       SELECT baz
       FROM foo
       WHERE fooID='1'
      )

其中foo 是主键fooID 的表名.bar 和 baz 是 INT 类型.执行此操作时出现以下错误:

Where foo is the table name with primary key fooID. bar and baz are of type INT. When executing this I get the following error:

Error: A query failed. You can't specify target table 'foo' for update 
in FROM clause

推荐答案

从此网络文章

这个错误的原因是当你在内部选择中使用同一个表作为更新条件时，MySQL 不允许更新表.文章接着提供了一个解决方案，即使用临时表.

The reason for this error is that MySQL doesn’t allow updates to a table when you are also using that same table in an inner select as your update criteria. The article goes on to provide a solution, which is to use a temporary table.

使用这个例子，你的更新应该是这样的:

Using this example, your update should be this:

update foo
set bar = bar - 1
where baz in
(
  select baz from
  (
    select baz
    from foo
    where fooID = '1'
  ) as arbitraryTableName
)

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