Question

I am using this query to insert data into two different tables:

    $query1="INSERT INTO node (cid, title) VALUES('$cid','$title')";
    $query2="INSERT INTO location (nid, street, city, state) VALUES(LAST_INSERT_ID(),'$address', '$city','$state')";
    $result = FALSE;
    if (mysql_query('BEGIN')) {
        if (mysql_query($query1) &&
        mysql_query($query2))
        $result = mysql_query('COMMIT'); // both queries looked OK, save
        else
        mysql_query('ROLLBACK'); // problems with queries, no changes
    }

basically, the first query throws the data into the node table which in turn increments a NID field. This NID is used in the second query (my location table).

Now I have changed my website a bit and I also want to insert that same NID into a 3rd table. The problem is the second query (location table) also has an ID column (LID) that auto_increments as well, so if I try to use last_insert_ID it will just give me the LID and not the NID.

I was thinking I could do a 3rd query outside of the transaction where I would query the database and grab the correct nid, but I want to keep it inside of a transaction to prevent any mixups. Any ideas?

Answer 1

The function LAST_INSERT_ID() is only guaranteed to work once.

Best practice is to capture this value in your code directly after the query you want it after, either with SELECT LAST_INSERT_ID() or by using mysqli_insert_id(). Then you can insert it into later queries with impunity.