insert into t2 values (1,repeat("a",1000)),(2,repeat("a",1000)),(3,repeat("b",1000)),(4,repeat("c",1000)),(4,repeat("b",1000));
SELECT GROUP_CONCAT(t1.language_id SEPARATOR ',') AS `translation_resources`, `d`.`serialized_c` FROM t2 AS `d` LEFT JOIN t1 ON `d`.`voter_id` = t1.`voter_id` GROUP BY `d`.`voter_id` ORDER BY 10-d.voter_id+RAND()*0;