MySQL calculate yyyy-mm-dd to days

Question

我目前有一列显示用户上次访问特定环境的时间，其格式为2015-01-26 15:35:45我需要能够以某种方式计算/转换格式，因此我可以确定用户在过去45天内访问了环境，并使用current_date作为计算日期。

Answer 1

You can use DATE_SUB to subtract 45 days from current date and compare that with values in your field ie

SELECT DATE_SUB(NOW(), INTERVAL 45 DAY)

which gives 2015-08-09 14:41:55 when executed on 2015-09-23 14:41:55 , hence your query becomes

SELECT * FROM table_name
WHERE last_login_dt > DATE_SUB(NOW(), INTERVAL 45 DAY)

OR

You can use DATEDIFF to subtract two dates, this will return the difference in days between the given dates

SELECT DATEDIFF(NOW(), '2015-09-01')

which gives 21 ie 2015-09-01 is 21 days before current date. So your query should look like

SELECT * FROM table_name
WHERE DATEDIFF(NOW(), last_login_dt) >= 45

assuming that name of your field with last login date is last_login_dt , please change as required

Answer 2

You could use str_to_date to convert the string to a date, and then use datediff to find the days between then and NOW() :

SELECT *
FROM   mytable
WHERE  DATEDIFF(CURRENT_DATE, STR_TO_DATE(last_login, '%Y-%m-%d %H-%i-%s')) >= 45