需求

在某些业务场景中，需要后台获取连续十二个月的统计数据，如下图：

解决方式

1、创建一张临时表，在表中插入序号数据

该表的最大数量决定统计返回的最大条数

CREATE TABLE `sys_redundancy` (
  `id` bigint(22) NOT NULL AUTO_INCREMENT COMMENT '序号',
  PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=1001 DEFAULT CHARSET=utf8 COMMENT='冗余必须表：目前用于用户注册统计，该表的数量决定用户统计返回的条数';

插入连续1000条数据

DROP PROCEDURE IF EXISTS proc_initData;
DELIMITER $
CREATE PROCEDURE proc_initData()
BEGIN
DECLARE i INT DEFAULT 1;
WHILE i<=1000 DO
INSERT INTO sys_redundancy(id) VALUES(i);
SET i = i+1;
END WHILE;
END $
DELIMITER ;

CALL proc_initData();

2、查询SQL

select * from(
SELECT
    IFNULL(count(a.user_id), 0) AS sum,
    b.tdate AS date
FROM
    sys_user a
RIGHT JOIN (
    SELECT
        DATE_FORMAT(DATE_SUB(CURDATE(), INTERVAL n.id-1 MONTH),'%Y-%m') AS tdate
    FROM
        sys_redundancy n 
) b ON DATE_FORMAT(a.create_time,'%Y-%m') = b.tdate and a.user_type = 2 
GROUP BY
    b.tdate
ORDER BY b.tdate desc
limit 12) m 
ORDER BY m.date asc
;