Sort MySQL result set using comparison between 2 columns of same value type

Question

Hello,

I have a table containing last_updated_1 and last_updated_2 columns, used respectively for text and images update time on a post.

I wish I could get a result set of 10 rows based on all time last updated records contained in the 2 columns, ex. row 1 = last_updated_1 record, row 2 = last_updated_2 record, row 3 = last_updated_1 record, etc.

How could I compare inside a MySQL query the both columns values, to get unique & mixed result set ?

Thank you in advance for your help

Answer 1

If I understand correctly your question, this should do it:

SELECT D.val, D.tstamp
FROM
(
    (
        SELECT val AS val, last_updated_1 AS tstamp
        FROM table_1
        ORDER BY tstamp
        LIMIT 50
    )

    UNION

    (
        SELECT val AS val, last_updated_2 AS tstamp
        FROM table_2
        ORDER BY tstamp
        LIMIT 50
    )
) AS D
ORDER BY D.tstamp
LIMIT 50;