mysql-按天/月统计数据,没有的填充为0

CREATE TABLE num (i INT);
INSERT INTO num (i) VALUES (0),(1),(2),(3),(4),(5),(6),(7),(8),(9);
 
-- 测试表
DROP TABLE IF EXISTS `user`;
CREATE TABLE `user` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `username` varchar(32) NOT NULL COMMENT '用户名称',
  `birthday` date DEFAULT NULL COMMENT '生日',
  `sex` char(1) DEFAULT NULL COMMENT '性别',
  `address` varchar(256) DEFAULT NULL COMMENT '地址',
  `sign_date` varchar(100) DEFAULT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=6 DEFAULT CHARSET=utf8;
INSERT INTO `user` VALUES ('1', '小南', '1991-04-04', '男', '湖南湘潭', '2018-03-13');
INSERT INTO `user` VALUES ('2', '小谭', '1981-01-27', '男', '湖南湘潭', '2018-03-12');
INSERT INTO `user` VALUES ('3', '小梅', '1981-04-28', '女', '广东梅县', '2018-04-14');
INSERT INTO `user` VALUES ('4', '小仪', '1986-04-12', '女', '四川仪陇', '2018-03-13');
INSERT INTO `user` VALUES ('5', '小蓝', '2001-01-01', '女', '上海嘉定', '2018-03-15');
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SELECT
	adddate('2018-03-01', numlist.id) AS 'date'
	FROM
	(
	SELECT
	n1.i + n10.i * 10 + n100.i * 100 AS id
	FROM
	num n1
	CROSS JOIN num AS n10
	CROSS JOIN num AS n100
	) AS numlist
	WHERE
	adddate('2018-03-01', numlist.id) <= date_add('2018-03-01',interval 1 month)
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SELECT left(sign_date,10)as udate,count(sign_date) unmber FROM user GROUP BY udate
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SELECT temp.date,
	coalesce(u.unmber,0) 'number' from(
	SELECT
	adddate('2018-03-01', numlist.id) AS 'date'
	FROM
	(
	SELECT
	n1.i + n10.i * 10 + n100.i * 100 AS id
	FROM
	num n1
	CROSS JOIN num AS n10
	CROSS JOIN num AS n100
	) AS numlist
	WHERE
	adddate('2018-03-01', numlist.id) <= date_add('2018-03-01',interval 1 month)) temp
LEFT JOIN 
(SELECT left(sign_date,10)as udate,count(sign_date) unmber FROM user GROUP BY udate) u on temp.date = u.udate order by temp.date
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SELECT left(temp.date,7),
	coalesce(u.unmber,0) 'number' from(
	SELECT adddate('2018-01-01', interval numlist.id month) AS 'date' FROM 
	(
	SELECT * from 
	(SELECT n1.i + n10.i * 10 AS id FROM num n1 CROSS JOIN num AS n10) a 
	where a.id<=11
		) AS numlist
	 WHERE adddate('2018-01-01', interval numlist.id month) <= '2018-12-01') temp
LEFT JOIN 
(SELECT left(sign_date,7)as udate,count(sign_date) unmber FROM user GROUP BY udate) u on left(temp.date,7) = u.udate ORDER BY temp.date
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