MySQL on duplicate key… get existing ID?

Question

I\'m using ON DUPLICATE KEY UPDATE to handle duplicate inserts on a table, in order that they are discarded.

In my case it\'s a simple table storing tags:

Answer 1

You could add a third column ModifiedDate and use that:

insert into t(id, tag)
    select id, tag
    on duplicate key update ModifiedDate = now();

This will ensure that an update really occurs, and in turn, that LAST_INSERT_ID() returns a value.