由左發現如何刪除記錄加入

Question

有了下面的查詢我能找到的數據我想刪除：

SELECT ab.id, ab.anlage_id, a.id 
FROM `anlagetobedienung` AS ab 
LEFT JOIN anlage_new AS a ON ab.`anlage_id` = a.id 
WHERE a.id IS NULL 

如何做我必須寫一個刪除在anlagetobedienung表中找到的記錄DELETE語句？

Answer 1

DELETE ab 
FROM `anlagetobedienung` AS ab 
LEFT JOIN anlage_new AS a ON ab.`anlage_id` = a.id 
WHERE a.id IS NULL 

Answer 2

通常我會說：

delete anlage_new 
where id in (
    SELECT a.id 
    FROM `anlagetobedienung` AS ab 
    LEFT JOIN anlage_new AS a ON ab.`anlage_id` = a.id 
    WHERE a.id IS NULL 
) 

即刪除該行，其中主鍵是在選擇的識別記錄刪除的結果。

但根據你的查詢，那些有id = NULL這似乎沒有任何意義。

您能否提供一些示例數據？

你的編輯後，我想說這應該工作：

delete `anlagetobedienung` 
where id in (
    SELECT ab.id 
    FROM `anlagetobedienung` AS ab 
    LEFT JOIN anlage_new AS a ON ab.`anlage_id` = a.id 
    WHERE a.id IS NULL 
) 

注：內選擇了「ab.id」，而不是「a.id」這似乎是在原來僅有的一列選擇有可能包含有用的東西。

Answer 3

DELETE FROM anlagebedienung aDEL WHERE aDEL.id IN 
(SELECT ab.id 
    FROM `anlagetobedienung` AS ab 
    LEFT JOIN anlage_new AS a ON ab.`anlage_id` = a.id 
    WHERE a.id IS NULL) 

Answer 4

另一種可能的解決方案：

DELETE FROM anlagetobedienung A 
WHERE 
    NOT EXISTS (SELECT * FROM anlage_new AN WHERE AN.id = A.anlage_id) 

如果MySQL支持別名，在DELETE FROM（在MS SQL的支持，但我知道，一些主要的RDBMS不支持這一點），那麼你可以做：

DELETE ab 
FROM 
    anlagetobedienung AS ab 
LEFT JOIN anlage_new AS a ON 
    ab.anlage_id = a.id 
WHERE 
    a.id IS NULL 

Answer 5

你可以簡單地做：

DELETE FROM anlagetobedienung ab 
WHERE NOT EXISTS (SELECT NULL 
        FROM anlage_new a 
        WHERE a.id = ab.anlage_id 
       )