id | venue_id | days
1  |   1      | 1,2,3
2  |   2      | 2,5
3  |   1      | 4

SELECT GROUP_CONCAT(batch_days SEPARATOR ", ") as daysid FROM `batch_list` WHERE `batch_venue_id` IN (1) GROUP BY `batch_venue_id`

1,2,3,4

SELECT GROUP_CONCAT(batch_days SEPARATOR ", ") as daysid FROM `batch_list` WHERE `batch_venue_id` IN (1) AND `batch_days` IN(2,3,5) GROUP BY `batch_venue_id`