MySQL get rows but prefer one column value over another

Question

A bit of a strange one, I want to write a MySQL query that will get results from a table, but prefer one value of a column over another, ie

id   name    value            


        

Answer 1

This should do it:

SELECT
     T1.id,
     T1.name,
     T1.value,
     T1.priority
FROM
     My_Table T1
LEFT OUTER JOIN My_Table T2 ON
     T2.name = T1.name AND
     T2.priority > COALESCE(T1.priority, -1)
WHERE
     T2.id IS NULL

This also allows you to have multiple priority levels with the highest being the one that you want to return (if you had a 1 and 2, the 2 would be returned).

I will also say though that it does seem like there are some design problems in the DB. My approach would have been:

My_Table (id, name) My_Values (id, priority, value) with an FK on id to id. PKs on id in My_Table and id, priority in My_Values. Of course, I'd use appropriate table names too.