scottlabs scottlabs - 2 months ago 28
MySQL Question

MySQL ON DUPLICATE KEY - last insert id?

I have the following query:

INSERT INTO table (a) VALUES (0)
ON DUPLICATE KEY UPDATE a=1


I want the ID of either the insert or the update. Usually I run a second query in order to get this as I believe insert_id() only returns the 'inserted' ID and not the updated ID.

Is there a way to INSERT/UPDATE and retrieve the ID of the row without running two queries?

Answer

Check this page out: http://dev.mysql.com/doc/refman/5.0/en/insert-on-duplicate.html
At the bottom of the page they explain how you can make LAST_INSERT_ID meaningful for updates by passing an expression to that MySQL function.

From the MySQL documentation example:

If a table contains an AUTO_INCREMENT column and INSERT ... UPDATE inserts a row, the LAST_INSERT_ID() function returns the AUTO_INCREMENT value. If the statement updates a row instead, LAST_INSERT_ID() is not meaningful. However, you can work around this by using LAST_INSERT_ID(expr). Suppose that id is the AUTO_INCREMENT column. To make LAST_INSERT_ID() meaningful for updates, insert rows as follows:

INSERT INTO table (a,b,c) VALUES (1,2,3)
  ON DUPLICATE KEY UPDATE id=LAST_INSERT_ID(id), c=3;