使用同一表的SubQuery更新

Question

是否可以使用同一表中的子查詢進行更新？

我收到此錯誤：

1093-您無法在FROM子句中指定目標表“任務”進行更新

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

我發現，如果將查詢包裝在另一個查詢中，它會起作用。 如此處所引用： MySQL錯誤1093-無法在FROM子句中指定目標表進行更新

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語句中支持JOIN，因此您可以執行此操作而無需子查詢。 您必須按照完成的條件加入到兩個不同的行中，以模擬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';