Summary: in this tutorial, you will learn how to use the MySQL
WEEK function to get the week number for a date.
Introduction to MySQL
Typically, a year has 365 days for a normal year and 366 days for leap year. A year is then divided into weeks with each week has exact 7 days. So for a year we often has 365 / 7 = 52 weeks that range from 1 to 52.
To check whether a particular date belongs to which week number, you use the
WEEK function as follows:
WEEK function accepts two arguments:
dateis the date that you want to get a week number.
modeis an optional argument that determines the logic of week number calculation. It allows you to specify whether the week should start on Monday or Sunday and the returned week number should be between 0 and 52 or 0 and 53.
If you ignore the
mode argument, the
WEEK function will use the value of the
default_week_format system variable by default.
To get the current value of
default_week_format variable, you use the
SHOW VARIABLES statement as follows:
mysql> SHOW VARIABLES LIKE 'default_week_format';
| Variable_name | Value |
| default_week_format | 0 |
1 row in set (0.01 sec)
In our server, the default value of
default_week_format is 0. The following table illustrates how the
mode argument influcences the
|Mode||First day of week||Range||Week 1 is the first week …|
|0||Sunday||0-53||with a Sunday in this year|
|1||Monday||0-53||with 4 or more days this year|
|2||Sunday||1-53||with a Sunday in this year|
|3||Monday||1-53||with 4 or more days this year|
|4||Sunday||0-53||with 4 or more days this year|
|5||Monday||0-53||with a Monday in this year|
|6||Sunday||1-53||with 4 or more days this year|
|7||Monday||1-53||with a Monday in this year|
with 4 or more days this year” in the above table means:
- If the week that contains January 1st and has 4 or more days in the new year, the week is numbered as week 1.
- Otherwise, the week is numbered as the last week of the previous year and the next week is week 1.
WEEK function returns a week number followed according to ISO 8601:1988
MySQL WEEK function example
See the following
orders table in the sample database.
The following statement returns the number of orders per week in 2013 using the
YEAR(orderDate) = 2003
GROUP BY WEEK(orderDate);
In this tutorial, you have learned how to use the MySQL
WEEK function to get the week number from a specified date.