MySQL刪除具有參數的行不存在ID

Question

我需要從表中刪除所有具有「for_id」參數的記錄引用此表中不存在的「id」。

In this example，我需要刪除name =「tom」的行，因爲id = 3的條目不存在。

謝謝！

Answer 1

DELETE D.* FROM table_name D 
    LEFT JOIN table_name T 
    ON T.ID=D.FOR_ID 
WHERE T.ID IS NULL and D.FOR_ID<>0; 

測試上sqlfiddle.com

Answer 2

所以，你要remove針對for_id確實在id
換句話說not exist這些記錄，keep那些其for_id確實exists在id

SELECT * FROM table_name 
where for_id in (select id from table_name) 

或記錄使用join：

SELECT t1.* FROM 
table_name t1 join table_name t2 
on t1.for_id=t2.id 

產量：

| id | for_id | lvl | name | 
|----|--------|-----|------| 
| 4 |  1 | 1 | joe | 
| 5 |  1 | 1 | mack | 
| 6 |  5 | 2 | bill | 
| 7 |  5 | 2 | rex | 
| 8 |  7 | 3 | ted | 

Answer 3

如果你想刪除已for_id = 0過那麼那些你可以使用：

DELETE 
FROM table_name as t1 
where not exists (select id 
     from table_name as t2 
     where t2.id=t1.for_id) 

，如果你不想刪除已for_id = 0您可以將那些用途：

delete 
FROM table_name as t1 
where not exists (select id 
     from table_name as t2 
     where t2.id=t1.for_id) and t1.for_id<>0