How Can I Efficiently Group Data by Week in MySQL?

Grouping Data by Week in MySQL

When working with timestamp values in MySQL, one may encounter a need to group data by week, similar to Oracle's TRUNC(timestamp,'DY') function. However, MySQL requires a different approach to achieve this functionality.

Using YEAR() and WEEK() Functions

MySQL offers the YEAR() and WEEK() functions, which can be used in conjunction to group data by week. By combining these functions in both the SELECT and GROUP BY clauses, one can achieve the desired result:

SELECT YEAR(timestamp), WEEK(timestamp), etc...
FROM ...
WHERE ..
GROUP BY YEAR(timestamp), WEEK(timestamp)

While not particularly elegant, this method is functional. Additionally, you can combine these functions to form a single expression:

SELECT CONCAT(YEAR(timestamp), '/', WEEK(timestamp)), etc...
FROM ...
WHERE ..
GROUP BY CONCAT(YEAR(timestamp), '/', WEEK(timestamp))

YEARWEEK() Function

Another option is to utilize the YEARWEEK() function, which returns a combined value of the year and week number:

SELECT YEARWEEK(mysqldatefield), etc...
FROM ...
WHERE ..
GROUP BY YEARWEEK(mysqldatefield)

This function provides a more compact output compared to the previous approach.

Straddling Weeks

It's important to consider the handling of weeks that straddle the beginning of the year. The YEAR() / WEEK() approach may split the aggregated data into two: one with the former year and one with the new year. In such cases, the YEARWEEK() function with an optional mode argument set to 0 or 2 ensures that the aggregated data includes complete weeks, regardless of straddling issues.

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