Application scenarios

When processing statistics about weekly data , There's a problem ： adopt MySQL Of week Function statistics “ Weeks ”, Than PHP Of date(“W”,time()) Acquired “ Weeks ” Small 1. Such as “2020-06-18 13:27:01”,MySQL What comes out is 24, and PHP What comes out is 25, This leads to a week of data not matching .

This is the first time I have encountered this problem , So I used it specially win10 The calendar in the corner counts , Find out “2020-06-18 13:27:01” It is 2020 In the first 25 Zhou , The problem is MySQL Of week Function .

The problem

Take a close look at , Find out MySQL Of week The function has a 2 Parameters ——mode？！

WEEK Two parameters of function ：

date Is to get the date of the week .

mode Is an optional parameter , The logic used to determine the calculation of the number of weeks . It allows you to specify whether this week starts on Monday or Sunday , The number of weeks returned should be in 0 To 52 Between or 0 To 53 Between .

After reading this note, I didn't understand it at first , But I looked at the following table ：

Suddenly I understood ！

By default ,mode Parameter extraction 0, in other words , Weeks are counted from Sunday , Look again “2020-06-18 13:27:01”, Actually , The week it is in is “2020-06-14” To “2020-06-20”, instead of “2020-06-15” To “2020-06-21”

That's clear , It is caused by the difference of the first day of the week , that , Only unify it , Just OK 了 .

Solution

stay MySQL Of week Add the second parameter to the function “1”, namely WEEK(created_at,1), Look again ,MySQL and PHP The weeks taken are the same ！

As for why there is 0-7 These eight models , Friends who understand , Welcome to leave a message ！ thank you ~