How to make a SQL query for last transaction of every account?

Question

Say I have a table \"transactions\" that has columns \"acct_id\" \"trans_date\" and \"trans_type\" and I want to filter this table so that I have just the last transaction f

Answer 1

Try this

WITH 
LastTransaction AS
(
    SELECT acct_id, max(trans_date) as trans_date  
    FROM transactions 
    GROUP BY acct_id
),
AllTransactions AS
(
    SELECT acct_id, trans_date, trans_type
    FROM transactions 
)
SELECT *
FROM AllTransactions
INNER JOIN LastTransaction
    ON AllTransactions.acct_id = LastTransaction.acct_id
    AND AllTransactions.trans_date  = LastTransaction.trans_date

Answer 2

This works on SQL Server...

SELECT acct_id, trans_date, trans_type
FROM transactions a
WHERE trans_date = (
   SELECT MAX( trans_date )
   FROM transactions b
   WHERE a.acct_id = b.acct_id
)

Answer 3

select t.acct_id, t.trans_type, tm.trans_date
from transactions t
inner join (
    SELECT acct_id, max(trans_date) as trans_date  
    FROM transactions 
    GROUP BY acct_id;
) tm on t.acct_id = tm.acct_id and t.trans_date = tm.trans_date

Answer 4

This is an example of a greatest-n-per-group query. This question comes up several times per week on StackOverflow. In addition to the subquery solutions given by other folks, here's my preferred solution, which uses no subquery, GROUP BY, or CTE:

SELECT t1.*
FROM transactions t1
LEFT OUTER JOIN transactions t2
  ON (t1.acct_id = t2.acct_id AND t1.trans_date < t2.trans_date)
WHERE t2.acct_id IS NULL;

In other words, return a row such that no other row exists with the same acct_id and a greater trans_date.

This solution assumes that trans_date is unique for a given account, otherwise ties may occur and the query will return all tied rows. But this is true for all the solutions given by other folks too.

I prefer this solution because I most often work on MySQL, which doesn't optimize GROUP BY very well. So this outer join solution usually proves to be better for performance.