Well, you asked for sql and ansi sql function is listagg(), so technically this is not the right answer - and definitely a completely useless one for mysql or oracle users.
MySQL: SELECT GROUP_CONCAT(columnName SEPARATOR ', ') FROM tableName;
Oracle: SELECT LISTAGG(columnName, ', ') WITHIN GROUP (ORDER BY columnName) FROM tableName;
I mean, it's not a big deal.. you just give have to give it a little nudge.
Well, you asked for sql and ansi sql function is listagg(), so technically this is not the right answer - and definitely a completely useless one for mysql or oracle users.