表字段包括:用户id,年,月,日
CREATE TABLE `a` (
`user_id` int(11) NOT NULL,
`day` int(10) NOT NULL,
`month` int(10) DEFAULT NULL,
`year` int(10) DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=latin1;
请查询在2020年每个月都有记录的用户id?
###SELECT
user_id
FROM
(SELECT
user_id
FROM
a
WHERE
year = 2020
GROUP BY user_id , month) b
GROUP BY user_id
HAVING COUNT(user_id) = 12;