MySQL Cookbook

Finding Dates for Weekdays of Other Weeks

Problem

You want to compute the date for some weekday of some other week.

Solution

Figure out the date for that weekday in the current week, then shift the result into the desired week.

Discussion

Calculating the date for a day of the week in some other week is a problem that breaks down into a day-within-week shift (using the formula given in the previous section) plus a week shift. These operations can be done in either order because the amount of shift within the week is the same whether or not you shift the reference date into a different week first. For example, to calculate Wednesday of a week by the preceding formula, n is 4. To compute the date for Wednesday two weeks ago, you can perform the day-within-week shift first, like this:

mysql> SET @target =
    -> DATE_SUB(DATE_ADD(CURDATE( ),INTERVAL 4-DAYOFWEEK(CURDATE( )) DAY),
    -> INTERVAL 14 DAY);
mysql> SELECT CURDATE( ), @target, DAYNAME(@target);
+------------+------------+------------------+
| CURDATE( )  | @target    | DAYNAME(@target) |
+------------+------------+------------------+
| 2002-07-15 | 2002-07-03 | Wednesday        |
+------------+------------+------------------+

Or you can perform the week shift first:

mysql> SET @target =
    -> DATE_ADD(DATE_SUB(CURDATE( ),INTERVAL 14 DAY),
    -> INTERVAL 4-DAYOFWEEK(CURDATE( )) DAY);
mysql> SELECT CURDATE( ), @target, DAYNAME(@target); +------------+------------+------------------+ | CURDATE( ) | @target | DAYNAME(@target) | +------------+------------+------------------+ ...