Question

This type of question is asked every now and then. The queries provided works, but it affects performance.

I have tried the JOIN method:

SELECT * 
FROM nbk_tabl
INNER JOIN (
        SELECT ITEM_NO, MAX(REF_DATE) as LDATE
        FROM nbk_tabl 
        GROUP BY ITEM_NO) nbk2 
ON nbk_tabl.REF_DATE = nbk2.LDATE 
AND nbk_tabl.ITEM_NO = nbk2.ITEM_NO

And the tuple one (way slower):

SELECT * 
FROM nbk_tabl
WHERE REF_DATE IN (
                    SELECT MAX(REF_DATE) 
                    FROM nbk_tabl 
                    GROUP BY ITEM_NO
                  )

Is there any other performance friendly way of doing this?

EDIT: To be clear, I’m applying this to a table with thousands of rows.

Answer 1

Yes, there is a faster way.

select *
from nbk_table
order by ref_date desc
limit <n>

Where is the number of rows that you want to return.

Hold on. I see you are trying to do this for a particular item. You might try this:

select *
from nbk_table n
where ref_date = (select max(ref_date) from nbk_table n2 where n.item_no = n2.item_no)

It might optimize better than the “in” version.