Mysql日常优化记录平时开发记录mysql的优化，提升程序的效能。日期加索引，快速筛选当天数据，速度差距在几十倍，意想

1、日期加索引，快速筛选当天数据

SELECT
        COUNT( 1 ) 
FROM
	md_member_heat a 
WHERE
	to_days( a.report_time ) = to_days(now()) AND a.platform_code = '' 
ORDER BY
	a.report_time DESC

## 时间大概是5.18s
	
SELECT
	COUNT( 1 ) 
FROM
	md_member_heat a 
WHERE
	 a.report_time > '2021-12-17 00:00:00' and a.report_time < '2021-12-18 00:00:00' AND a.platform_code = '' 
ORDER BY
	a.report_time DESC
## 时间大概是0.027s