JD Isaacks JD Isaacks - 1 year ago 75
MySQL Question

How to find duplicates in 2 columns not 1

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.

can have duplicates as long as for each
title is different, and in reverse. But say for example
= 412 and
= "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 Source

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