Delete from two tables in one query

user_111279 0
Viewed 485819

I have two tables in MySQL 

#messages table  : 
messageid
messagetitle 
.
.

#usersmessages table 
usersmessageid 
messageid
userid
.
.

Now if I want to delete from messages table it's ok. But when I delete message by messageid the record still exists on usersmessage and I have to delete from this two tables at once.

I used the following query : 

DELETE FROM messages LEFT JOIN usersmessages USING(messageid) WHERE messageid='1' ;

Then I test 

   DELETE FROM messages , usersmessages 
   WHERE messages.messageid = usersmessages.messageid 
   and messageid='1' ;

But these two queries are not accomplishing this task .

mysql sql
11 Answers

Can't you just separate them by a semicolon?

Delete from messages where messageid = '1';
Delete from usersmessages where messageid = '1'

OR

Just use INNER JOIN as below

DELETE messages , usersmessages  FROM messages  INNER JOIN usersmessages  
WHERE messages.messageid= usersmessages.messageid and messages.messageid = '1'
user_1036170

You should either create a FOREIGN KEY with ON DELETE CASCADE:

ALTER TABLE usersmessages
ADD CONSTRAINT fk_usermessages_messageid
FOREIGN KEY (messageid)
REFERENCES messages (messageid)
ON DELETE CASCADE

, or do it using two queries in a transaction:

START TRANSACTION;;

DELETE
FROM    usermessages
WHERE   messageid = 1

DELETE
FROM    messages
WHERE   messageid = 1;

COMMIT;

Transaction affects only InnoDB tables, though.

user_551590

You have two options:

First, do two statements inside a transaction:

BEGIN;
  DELETE FROM messages WHERE messageid = 1;
  DELETE FROM usermessages WHERE messageid = 1;
COMMIT;

Or, you could have ON DELETE CASCADE set up with a foreign key. This is the better approach.

CREATE TABLE parent (
  id INT NOT NULL,
    PRIMARY KEY (id)
);

CREATE TABLE child (
  id INT, parent_id INT,
  FOREIGN KEY (parent_id) REFERENCES parent(id) ON DELETE CASCADE
);

You can read more about ON DELETE CASCADE here.

user_1176030

The OP is just missing the table aliases after the delete

DELETE t1, t2 
FROM table1 t1 LEFT JOIN table2 t2 ON t1.id = t2.id 
WHERE t1.id = some_id
user_104280590 
DELETE message.*, usersmessage.* from users, usersmessage WHERE message.messageid=usersmessage.messageid AND message.messageid='1'
user_29568040

Try this..

DELETE a.*, b.*  
FROM table1 as a, table2 as b  
WHERE a.id=[Your value here] and b.id=[Your value here]

I let id as a sample column.

Glad this helps. :)

user_87034230

there's another way which is not mentioned here (I didn't fully test it's performance yet), you could set array for all tables -> rows you want to delete as below

// set your tables array
$array = ['table1', 'table2', 'table3'];


// loop through each table
for($i = 0; $i < count($array); $i++){

 // get each single array
 $single_array = $array[$i];

 // build your query
 $query = "DELETE FROM $single_array WHERE id = 'id'";

 // prepare the query and get the connection
 $data = con::GetCon()->prepare($query);

 // execute the action
 $data->execute();
}

then you could redirect the user to the home page.

header('LOCATION:' . $home_page);

hope this will help someone :)

Thanks

user_29960230
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