MySql 时间查询条件,索引优化

首先添加索引:

#添加索引  
ALTER TABLE `user` ADD INDEX create_time_index ( `create_time` ) 

错误做法:

1.

#  耗时 2.05
SELECT
	*
FROM
	user
WHERE
	DATE_FORMAT(create_time , '%Y-%m-%d') = '2021-01-21';

2.

#  耗时  1.58  
SELECT
	*
FROM
	user
WHERE
	to_days(create_time) = to_days(now());

3.

# 耗时 1.68 
SELECT
	*
FROM
	user
WHERE
	date(create_time) = curdate();

curdate() --------函数返回当前的日期
date()    --------函数返回当前时间的日期部分

正确做法:

1.

# 添加索引前 3.24 3.76 
# 添加索引后  查询时间为 0 秒
SELECT
	*
FROM
	user
WHERE
	create_time BETWEEN CONCAT(curdate() , ' 00:00:00')
AND CONCAT(CURDATE() , ' 23:59:59')

2.

# 添加索引前1.63  1.61   
# 添加索引后  查询时间为 0 秒
SELECT
	*
FROM
	user
WHERE
	create_time >= '2021-01-21'
AND create_time < '2021-01-22'

3.

# 添加索引前 1.74 1.77    
# 添加索引后  查询时间为 0 秒
SELECT
	*
FROM
	user
WHERE
	create_time BETWEEN '2021-01-21 00:00:00'
AND '2021-01-21 23:59:59';