GROUP_CONCAT change GROUP BY order

Question

I have a VIEW (lots of joins) that outputs data ordered by a date ASC. Works as expected.

OUTPUT similar to:

ID date         tag         


        

Answer 1

Looks like GROUP_CONCAT no longer preserves the VIEW order. Is this normal?

Yes, it is normal.

You should not rely, ever, on the order in which ungrouped and unaggregated fields are returned.

GROUP_CONCAT has its own ORDER BY clause which the optimizer takes into account and can change the order in which is parses the records.

To return the first record along with GROUP_CONCAT, use this:

SELECT  m.*, gc
FROM    (
        SELECT  id, MIN(date) AS mindate, GROUP_CONCAT(tags) AS gc
        FROM    myview
        GROUP BY
                id
        ) md
JOIN    m.*
ON      m.id = md.id
        AND m.date = md.mindate