How to Find the First Day of a Given Week Number in MySQL?

Fetching the First Day of the Week in MySQL Based on Week Number

Determining the first day of a specific week using its week number is a common task in database programming. With MySQL's powerful date functions, this can be efficiently accomplished.

The Challenge:

Given a week number, how do we retrieve the first day of that week in MySQL? For instance, knowing that we are currently in WEEK 29, we seek to extract Sunday, July 18th from the provided week number parameter.

The Solution:

MySQL offers a straightforward approach to address this issue. Utilizing the DAYOFWEEK() function, we can determine the current weekday, ranging from 1 (Sunday) to 7 (Saturday). By subtracting the DAYOFWEEK() value from 1, we calculate the number of days since the previous Sunday.

Using the ADDDATE() function, we can then subtract the calculated number of days from the current date to arrive at the first day of the week:

ADDDATE(CURDATE(), INTERVAL 1-DAYOFWEEK(CURDATE()) DAY) WeekStart

With this query, we can obtain the first day of the week based on the current date. To further extend this logic to any given week number, we can parameterize the week number in the query:

ADDDATE(CURDATE(), INTERVAL 1-DAYOFWEEK(CURDATE())+(7 * (WEEKNO - WEEK(CURDATE()))) DAY) WeekStart

This query will return the first day of the week for the specified WEEKNO parameter. In this example, replacing WEEKNO with 29 yields the desired result: Sunday, July 18th.

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