Returns the week number of the year from a date .
Syntax
WEEK(date,[mode])
Example
SELECT WEEK('2015-07-25')
Output is 29
For a invalid date we will get Null as output
SELECT WEEK('2015-02-31')
Output is NULL
Understanding Mode (Optional Parameter , value 0 to 7)
The week can start on Sunday or Monday,
The week of 1st of Jan should have 4 more days to qualify for week No. 1
Otherwise it will be last week of previous year and next week will be No. 1
In the DEMO page for WEEK() try these days to understand the concepts of Mode.
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