Both previous replies are definitely on the mark. To follow up on the second one (and provide the missing detail that was not mentioned there): you want your "ON DUPLICATE KEY UPDATE ..." clause to include a reference to the primary key field -- something like this, assuming the "field_three" part is still needed: 
        . " ON DUPLICATE KEY"
        . " UPDATE field_three = ?, your_key_field=LAST_INSERT_ID(your
+_key_field)";

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I've always found this syntax to be a little disorienting, but you just have to accept the fact that when trying to insert a record that would violate some uniqueness constraint, the application of that constraint leaves the "last_insert_id" value "not meaningful". Check the last paragraph in section 12.2.4.3 of the mysql manual for an explanation (if you're using mysql), or the corresponding doc of your particular rdb server.

In reply to Re: DBI and last_insert_id by graff
in thread DBI and last_insert_id by cog

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