PostgreSQL - fetch the row which has the Max value for a column

Question

I\'m dealing with a Postgres table (called \"lives\") that contains records with columns for time_stamp, usr_id, transaction_id, and lives_remaining. I need a query that wil

Answer 1

I like the style of Mike Woodhouse's answer on the other page you mentioned. It's especially concise when the thing being maximised over is just a single column, in which case the subquery can just use MAX(some_col) and GROUP BY the other columns, but in your case you have a 2-part quantity to be maximised, you can still do so by using ORDER BY plus LIMIT 1 instead (as done by Quassnoi):

SELECT * 
FROM lives outer
WHERE (usr_id, time_stamp, trans_id) IN (
    SELECT usr_id, time_stamp, trans_id
    FROM lives sq
    WHERE sq.usr_id = outer.usr_id
    ORDER BY trans_id, time_stamp
    LIMIT 1
)

I find using the row-constructor syntax WHERE (a, b, c) IN (subquery) nice because it cuts down on the amount of verbiage needed.