MySQL从多个表中删除行

Question

I have 2 tables users and pd having a common column i_uid

For deleting from both the tables a single row having i_uid of 1010 I issued the following statement using mysqli::query in php script

DELETE 
FROM `users`,`pd`
WHERE `users`.`i_uid`=`pd`.`i_uid` AND `users`.`i_uid` = 1010;

Is there anything wrong?

Answer 1

since you are deleting rows from multiple table, the only missing is to specify on what tables the row will be deleted,

DELETE `users`,`pd`
FROM `users`, `pd`
WHERE `users`.`i_uid`=`pd`.`i_uid` AND `users`.`i_uid` = 1010;

in the query above, it will delete rows from both tables. I suggest to change statement using ANSI join like below,

DELETE  a, b 
FROM    users a
        INNER JOIN pd b
            ON a.i_uid = b.i_uid
WHERE  a.i_uid = 1010

if you want to delete from users table,

DELETE  a
FROM    users a
        INNER JOIN pd b
            ON a.i_uid = b.i_uid
WHERE  a.i_uid = 1010

Answer 2

Use Left Join and specify the tables on which corresponding rows will be deleted.

DELETE users, pd
FROM users, pd
LEFT JOIN pd
ON pd.i_uid = users.i_uid
WHERE users.i_uid = 1010

Answer 3

Other answers are correct but since no one mentioned it I will. You could use InnoDB engine and specify foreign keys and DELETE ON CASCADE . So that each time you delete a user it will delete all referencing rows from different tables.

Read up on Foreign Keys and DELETE ON CASCADE

Answer 4

To keep it simple I suggest using just two queries:

DELETE FROM `users` WHERE `i_uid` = 1010;
DELETE FROM `pd` WHERE `i_uid` = 1010;