Question

I have a MySQL database table with two columns that interest me. Individually they can each have duplicates, but they should never have a duplicate of BOTH of them having the same value.

stone_id can have duplicates as long as for each upsharge title is different, and in reverse. But say for example stone_id = 412 and upcharge_title = ‘sapphire’ that combination should only occur once.

This is ok:

stone_id = 412 upcharge_title = 'sapphire' stone_id = 412 upcharge_title = 'ruby' 

This is NOT ok:

stone_id = 412 upcharge_title = 'sapphire' stone_id = 412 upcharge_title = 'sapphire' 

Is there a query that will find duplicates in both fields? And if possible is there a way to set my data-base to not allow that?

I am using MySQL version 4.1.22

Answer 1

You should set up a composite key between the two fields. This will require a unique stone_id and upcharge_title for each row.

As far as finding the existing duplicates try this:

select   stone_id,          upcharge_title,          count(*) from     your_table group by stone_id,          upcharge_title having   count(*) > 1