MySQL的DELETE FROM與子查詢的條件

Question

我試圖做一個查詢這樣的：

DELETE FROM term_hierarchy AS th 
WHERE th.parent = 1015 AND th.tid IN (
    SELECT DISTINCT(th1.tid) 
    FROM term_hierarchy AS th1 
    INNER JOIN term_hierarchy AS th2 ON (th1.tid = th2.tid AND th2.parent != 1015) 
    WHERE th1.parent = 1015 
); 

正如你可能會說，我想刪除父關係1015是否相同TID有其他家長。但是，我得到一個語法錯誤：

You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'AS th 
WHERE th.parent = 1015 AND th.tid IN (
    SELECT DISTINCT(th1.tid) 
    FROM ter' at line 1 

我已經檢查的文件，並通過自身運行子查詢，而這一切似乎退房。任何人都可以弄清楚這裏有什麼問題嗎？

更新：如下面的回答，MySQL不允許將您要刪除的表用於條件的子查詢中。

Answer 1

您不能指定目標表刪除。

一種解決方法

create table term_hierarchy_backup (tid int(10)); <- check data type 

insert into term_hierarchy_backup 
SELECT DISTINCT(th1.tid) 
FROM term_hierarchy AS th1 
INNER JOIN term_hierarchy AS th2 ON (th1.tid = th2.tid AND th2.parent != 1015) 
WHERE th1.parent = 1015; 

DELETE FROM term_hierarchy AS th 
WHERE th.parent = 1015 AND th.tid IN (select tid from term_hierarchy_backup); 

Answer 2

您需要在delete語句中再次引用別名，如：

DELETE th FROM term_hierarchy AS th 
.... 

As outlined here in MySQL docs.

Answer 3

別名應包含在DELETE關鍵字後：

DELETE th 
FROM term_hierarchy AS th 
WHERE th.parent = 1015 AND th.tid IN 
(
    SELECT DISTINCT(th1.tid) 
    FROM term_hierarchy AS th1 
    INNER JOIN term_hierarchy AS th2 ON (th1.tid = th2.tid AND th2.parent != 1015) 
    WHERE th1.parent = 1015 
); 

Answer 4

對於其他人發現這個問題看，同時使用子查詢，刪除，我離開你這個例子超過MySQL（即使有些人似乎認爲它不能完成）：

DELETE e.* 
FROM tableE e 
WHERE id IN (SELECT id 
      FROM tableE 
      WHERE arg = 1 AND foo = 'bar'); 

會給你一個錯誤：

ERROR 1093 (HY000): You can't specify target table 'e' for update in FROM clause 

但此查詢：

DELETE e.* 
FROM tableE e 
WHERE id IN (SELECT id 
      FROM (SELECT id 
        FROM tableE 
        WHERE arg = 1 AND foo = 'bar') x); 

會工作得很好：

Query OK, 1 row affected (3.91 sec) 

環繞你的子查詢了在其他子查詢（這裏命名爲x） MySQL會很樂意做你所要求的。

Answer 5

我以一種稍微不同的方式接近這個，它對我有用;

我需要從我的表中刪除secure_links引用conditions表，其中不再有任何條件行左。一個家政腳本基本上。這給了我錯誤 - 你不能指定目標表進行刪除。

所以在這裏尋找靈感我想出了下面的查詢，它工作得很好。 這是因爲它創建了一個用作DELETE參考的臨時表sl1。

DELETE FROM `secure_links` WHERE `secure_links`.`link_id` IN 
      (
      SELECT 
       `sl1`.`link_id` 
      FROM 
       (
       SELECT 

        `sl2`.`link_id` 

       FROM 
        `secure_links` AS `sl2` 
        LEFT JOIN `conditions` ON `conditions`.`job` = `sl2`.`job` 

       WHERE 

        `sl2`.`action` = 'something' AND 
        `conditions`.`ref` IS NULL 
       ) AS `sl1` 
      ) 

適合我。

Answer 6

是不是刪除中的「in」子句...如果從子查詢中返回大量的值，效率極低？不知道爲什麼你不會爲了刪除而不是內部（或右邊）從子查詢中反向刪除原始表，而不是我們的「in（subquery）」。

DELETE T FROM Target AS T 
RIGHT JOIN (full subquery already listed for the in() clause in answers above) ` AS TT ON (TT.ID = T.ID) 

也許它是在回答「MySQL不允許它」，但是，它工作正常，我提供的我一定要完全弄清楚刪除的內容（DELETE FROM牛逼目標AS T）。 Delete with Join in MySQL闡明DELETE/JOIN問題。

Answer 7

如果你想與2個查詢要做到這一點，你總是可以做同樣的事情到這一點：

1）抓住IDS從表：

SELECT group_concat(id) as csv_result FROM your_table WHERE whatever = 'test' ... 

然後複製用鼠標/鍵盤導致或編程語言爲XXX：

2) DELETE FROM your_table WHERE id IN (XXX) 

也許你可以在一個查詢中做到這一點，但這是我更喜歡的。