sql - 我如何重写此查询以避免错误 : You can't specify target table for update in FROM clause

Question

update websites set master = 2 where url = select url from websites where id = 12;

显然 mysql 不允许您对正在更新的表运行选择查询。

Answer 1

将其放入派生表中。 This gets materialised into a temp table and gets around the restriction .

update websites
set    master = 2
where  url in (select url
               from   (select url
                       from   websites
                       where  id = 12) t);