using group_concat in PHPMYADMIN will show the result as [BLOB - 3B]
Looks as though GROUP_CONCAT expects that value to be a string. I just ran into the same problem. Solved it by converting the int column to a string like so:
SELECT rec_id,GROUP_CONCAT(CONVERT(user_id, CHAR(8)))FROM t1GROUP BY rec_idFigured I'd share in case you were still having an issue with this.
According to the MySQL documentation, CAST(expr AS type) is standard SQL and should thus be perferred. Also, you may omit the string length. Therefore, I’d suggest the following:
SELECT rec_id, GROUP_CONCAT(CAST(user_id AS CHAR))FROM t1GROUP BY rec_id
For me, this helped (found it in this blog post):
In my case the parameter to GROUP_CONCAT was string but the function still resulted in a BLOB, but converting the result of the GROUP_CONCAT worked.
CONVERT(GROUP_CONCAT(user_id) USING 'utf8')