本查询是计算两个表的相同时间(天)的记录数

1.合并就用UNION ALL

第一个查询:

SELECT 
DATE_FORMAT(BIND_TIME,'%Y-%m-%d') time, 
count(*) 
FROM bind_hist 
GROUP BY time

SELECT  
DATE_FORMAT(BIND_TIME,'%Y-%m-%d') time, 
count(*) 
FROM bind_failed  
GROUP BY time

合并后为:

SELECT 
	DATE_FORMAT(BIND_TIME,'%Y-%m-%d') time, 
	0 as failed, 
	count(*) hist 
FROM bind_hist 
GROUP BY time 
UNION ALL 
SELECT  
	DATE_FORMAT(BIND_TIME,'%Y-%m-%d') time, 
	count(*) failed, 
	0 
FROM bind_failed  
GROUP BY time

2.将合并后的结果作为一个表,再根据时间GROUP BY,求和值

SELECT  
	r.time, 
	SUM(r.failed), 
	SUM(r.hist)  
FROM ( 
	SELECT 
		DATE_FORMAT(BIND_TIME,'%Y-%m-%d') time, 
		0 as failed, 
		count(*) hist 
	FROM bind_hist 
	GROUP BY time 
	UNION ALL 
	SELECT  
		DATE_FORMAT(BIND_TIME,'%Y-%m-%d') time, 
		count(*) failed, 
		0 
	FROM bind_failed  
	GROUP BY time 
) r 
GROUP BY r.time