SQL查询今天是否是数据库日期之前的X天

Question

I am using this SQL Query:

SELECT * from reminders where status <> 'c' AND user = '".$InternalUserResult["sequence"]."' AND duedate_date = '".date("Y-m-d")."' ";

it selects rows from a table based on the status and if the duedate_date is set today

i have 3 other columns in the table called duedate_time , remind_user_1 and remind_user_2

lets say in this example

remind_user_1 = 4
remind_user_2 = days

how can i add into my query *if today is 4 days before the due date *

and as another example,

remind_user_1 = 1
remind_user_2 = hour

the query i want to say:

if today is 1 hour before the duedate_date + duedatetime

Answer 1

The DATEDIFF function can be used in the where clause. In this case, the additional condition looks like:

AND DATEDIFF(duedate_date,CURDATE()) = 4

Answer 2

To get 4 days before date use SUBDATE function in mysql. eg

SELECT SUBDATE(NOW(),4);