Explain Query (mysql)
EXPLAIN SELECT `coupon`.`coupon_id` AS `t1_c0`, `coupon`.`name` AS `t1_c1`, `coupon`.`code` AS `t1_c2`, `coupon`.`type` AS `t1_c3`, `coupon`.`use_type` AS `t1_c4`, `coupon`.`amount` AS `t1_c5`, `coupon`.`created` AS `t1_c6`, `coupon`.`updated` AS `t1_c7`, `coupon`.`start_date` AS `t1_c8`, `coupon`.`end_date` AS `t1_c9`, `coupon`.`max_user_uses` AS `t1_c10`, `coupon`.`max_uses` AS `t1_c11`, `coupon`.`status` AS `t1_c12`, `coupon`.`note` AS `t1_c13`, `coupon`.`staff_id` AS `t1_c14`, `coupon`.`company_id` AS `t1_c15`, `coupon`.`up_to_amount` AS `t1_c16`, `coupon`.`for_new` AS `t1_c17`, `coupon`.`referrer_user_id` AS `t1_c18`, `coupon`.`open_pup` AS `t1_c19`, `coupon`.`query` AS `t1_c20`, `coupon`.`product_id` AS `t1_c21`, `coupon`.`child_coupon_id` AS `t1_c22`, `coupon`.`gift_certificate` AS `t1_c23`, `coupon`.`used_for` AS `t1_c24`, `coupon`.`coupon_receiver_id` AS `t1_c25` FROM `coupons` `coupon` WHERE (`coupon`.`coupon_id`=NULL)
| id | select_type | table | partitions | type | possible_keys | key | key_len | ref | rows | filtered | Extra |
|---|---|---|---|---|---|---|---|---|---|---|---|
| 1 | SIMPLE | no matching row in const table |