MySQL统计近一个月每天的数量没有则显示为0

先上代码：

SELECT lefttable.date,IFNULL(righttable.m,'0') as total
	FROM
	(SELECT date_sub(CURDATE(),interval @i:=@i+1 day) as date
	from (select 1 union all select 1 union all select 1 union all select 1 union all select 1 union all select 1 union all select 1 union all select 1 union all select 1 union all select 1 union all select 1 union all select 1 union all select 1 union all select 1 union all   select 1 union all select 1 union all select 1 union all select 1 union all select 1 union all select 1 union all select 1 union all  select 1 union all select 1 union all select 1 union all select 1 union all select 1 union all select 1 union all select 1 union all  select 1 union all select 1) as tmp,(select @i:= -1) t) as lefttable
	LEFT JOIN
	(SELECT count(*)as m,DATE_FORMAT(tab2.CREATED_DATE,'%Y-%m-%d') as gptime
	from tb1 tab2
	where tab2.DOCTOR_ID=#{doctorId} and DATE(tab2.CREATED_DATE)>=DATE_SUB(CURDATE(), INTERVAL 29 DAY) GROUP BY gptime)
	as righttable
	ON lefttable.date=righttable.gptime ORDER BY lefttable.date;

思路：左边表格用了29个select 1 union all 作为临时表格来辅助获得近一个月的日期，右边表格查询近一个月的数据，然后进行联合查询，从而获得近一个月每天的数量。查询结果如下：

如果只要月-日，不要年份，只需要把开头的lefttable.date换成 DATE_FORMAT(lefttable.date,'%m-%d')as date即可，

如果要查询近半个月每天的数量，只要保留14个select 1 union all，同时把SQL中的29换成14即可。