MySQL: How to calculate weeks out from a specific date?

Question

I need to calculate the weeks out from a date in my MySQL select statement. There is a date column in one of the tables, and I need to calculate how many weeks away the date is.

SELECT EventDate, (calculation) AS WeeksOut FROM Events;

Example:

• 6 days away, weeks out = 0
• 7 days away, weeks out = 1
• 13 days away, weeks out = 1
• 14 days away, weeks out = 2

Answer 1

Use the DATEDIFF function:

ROUND(DATEDIFF(end_date, start_date)/7, 0) AS weeksout

The problem with WEEKS is that it won't return correct results for dates that cross over January 1st.

The 0 is the number of decimal places to use in the ROUND function.

Answer 2

In order to get past the whole "New Year" issue and you still want to use WEEK(), I found the following method quite effective.

SELECT 
    YEAR(end_date)*52+WEEK(end_date)
    - YEAR(start_date)*52 - WEEK(start_date) as weeks_out
FROM
    events;

The difference with this method (as opposed to the DATEDIFF method) is that it is aligned with the week. So today (which is Monday) and last Friday would return 1 using this method, but would return 0 with the DATEDIFF method