Question

I have a table that looks something like this:

________________________
|id|value|date|approved|
-----------------------

What I need to be able to do is get each row where approved = 1. That part is obvious. For each occurrence of value, I only want the most recent row (sorted by date).

Meaning that with a table like this:

________________________
|id|value|date|approved|
-----------------------
|1 |Foo  | 5  |   1    |
|2 |Bar  | 6  |   1    |
|3 |Foo  | 8  |   1    |
-----------------------

I only want the rows with id 2 and 3.

I assume I need to use DISTINCT somehow, but I’m not sure how. Could anyone help me out here?

Answer 1

SELECT  m.*
FROM    (
        SELECT  DISTINCT value
        FROM    mytable
        ) md
JOIN    mytable m
ON      m.id =
        (
        SELECT  id
        FROM    mytable mi
        WHERE   mi.value = md.value
                AND mi.approved = 1
        ORDER BY
                mi.value DESC, mi.date DESC, mi.id DESC
        LIMIT 1
        )

Create an index on (value, date, id) for this to work fast.