如何选择字段mysql中最后日期之前的最后n个月？

Question

I have a question with mysql. I have a table like records and records have a field registered_date which contains the dates. I want to select last n months but not before the current date. I must select the last date that registered_date contains.

registered_date

• 2015-05-30
• 2015-05-29
• 2015-05-28
• 2015-05-27
• ...

and we are in july. The last date is 2015-05-30. I want to select last 3 months before the 2015-05-30.

I tried to like these:

 .... where registered_date > DATE_SUB(now(), INTERVAL 6 MONTH)

and

registered_Date between now() - interval 30 day and now()

Thank you.

Answer 1

You need to find the biggest date and then select three months before that:

select t.*
from table t cross join
     (select max(registered_date) as maxrd from table t) m
where t.registered_date >= maxrd - interval 3 month;

Answer 2

你这样尝试过吗

SELECT * FROM table WHERE registered_date >= now()-interval 3 month;