Returning the 'last' row of each 'group by' in MySQL

Question

Is there a more efficient way of doing the following?

select * 
    from foo as a
    where a.id = (select max(id) from foo where uid = a.uid group by uid)
          


        

Answer 1

if table is big in size. Make view containing all last row id

create view lastrecords as (select max(id) from foo where uid = a.uid group by uid)

Now join your main query with this view. It will be faster.

  SELECT t1.* FROM tablename as t1
    JOIN lastrecords as  t2
    ON t1.id = t2.id AND t1.uid = t2.uid;

OR You can do join with last records direct in query also:

SELECT t1.* FROM tablename as t1
JOIN (SELECT uid, MAX(id) id FROM tablename GROUP BY id) as  t2
ON t1.id = t2.id AND t1.uid = t2.uid;