MySQL LAST_INSERT_ID() used with multiple records INSERT statement

Question

If I insert multiple records with a loop that executes a single record insert, the last insert id returned is, as expected, the last one. But if I do a multiple records inse

Answer 1

This behavior is mentioned on the man page for MySQL. It's in the comments but is not challenged, so I'm guessing it's the expected behavior.

Answer 2

I think it's possible if your table has unique autoincrement column (ID) and you don't require them to be returned by mysql itself. I would cost you 3 more DB requests and some processing. It would require these steps:

1. Get "Before MAX(ID)" right before your insert:

    SELECT MAX(id) AS before_max_id FROM table_name`

2. Make multiple INSERT ... VALUES () query with your data and keep them:

   INSERT INTO table_name
   (col1, col2)
   VALUES 
   ("value1-1" , "value1-2"), 
   ("value2-1" , "value2-2"), 
   ("value3-1" , "value3-2"), 
   ON DUPLICATE KEY UPDATE
   

3. Get "After MAX(ID)" right after your insert:

   SELECT MAX(id) AS after_max_id FROM table_name`
   

4. Get records with IDs between "Before MAX(ID)" and "After MAX(ID)" including:

   SELECT * FROM table_name WHERE id>$before_max_id AND id<=$after_max_id`
   

5. Do a check of retrieved data with data you inserted to match them and remove any records that were not inserted by you. The remaining records have your IDs:

    foreach ($after_collection as $after_item) {
      foreach ($input_collection as $input_item) {
        if ( $after_item->compare_content($input_item) ) {
          $intersection_array[] = $after_item;
        }
      }
    }

This is just how a common person would solve it in a real world, with parts of code. Thanks to autoincrement it should get smallest possible amount of records to check against, so they will not take lot of processing. This is not the final "copy & paste" code - eg. you have to create your own function compare_content() according you your needs.

Answer 3

Yes. This behavior of last_insert_id() is documented in the MySQL docs:

Important
If you insert multiple rows using a single INSERT statement, LAST_INSERT_ID() returns the value generated for the first inserted row only. The reason for this is to make it possible to reproduce easily the same INSERT statement against some other server.