使用同一表的SubQuery更新

Question

是否可以使用同一表中的子查询进行更新？

我收到此错误：

1093-您无法在FROM子句中指定目标表“任务”进行更新

update tasks SET completed_form = 'y' AND all_forms_in = 'y' where EID in (select EID from tasks WHERE completed_form = 'y' AND all_forms_in = 'n' group by EID having count(*) > 1);

UPDATE

我发现，如果将查询包装在另一个查询中，它会起作用。 如此处所引用： MySQL错误1093-无法在FROM子句中指定目标表进行更新

update tasks SET all_forms_in = 'y' where EID in (SELECT * FROM (select EID from tasks WHERE completed_form = 'y' AND all_forms_in = 'n' group by EID having count(*) > 1)AS b);

Answer 1

MySQL在UPDATE语句中支持JOIN，因此您可以执行此操作而无需子查询。 您必须按照完成的条件加入到两个不同的行中，以模拟count（*）> 1。

UPDATE tasks AS t1
INNER JOIN tasks AS t2
  ON (t1.EID = t2.EID AND t2.completed_form = 'y' AND t2.all_forms_in = 'n')
INNER JOIN tasks AS t3
  ON (t1.EID = t3.EID AND t3.completed_form = 'y' AND t3.all_forms_in = 'n'
  AND t2.primary_key <> t3.primary_key)
SET t1.completed_form = 'y', 
    t1.all_forms_in = 'y';