How to Calculate Week Start and End Dates from a Week Number in SQL?

Getting Week Start and End Dates from Week Number in SQL

In a scenario where you have a query that calculates the wedding counts for members grouped by year and week number, it is helpful to determine the start and end dates for each week.

To achieve this, you can incorporate calculations based on the day of week and use the DATEADD function.

Answer:

You can use the following expressions to calculate the week start and week end dates:

• Week Start: DATEADD(dd, -(DATEPART(dw, WeddingDate)-1), WeddingDate)
• Week End: DATEADD(dd, 7-(DATEPART(dw, WeddingDate)), WeddingDate)

Explanation:

• DATEPART(dw, WeddingDate): Returns the day of week for the WeddingDate (1=Sunday, 7=Saturday).
• -(DATEPART(dw, WeddingDate)-1): Subtracts the day of week (minus 1) to get the number of days before the start of the week (e.g., if it's Wednesday, subtract 2).
• DATEADD(dd, ...): Adds the specified number of days to the WeddingDate (e.g., adding 2 days to Wednesday gives Monday).

Example:

If the WeddingDate is '2023-03-08' (Wednesday), the calculations would be:

• Week Start: DATEADD(dd, -(DATEPART(dw, '2023-03-08')-1), '2023-03-08') = '2023-03-06' (Monday)
• Week End: DATEADD(dd, 7-(DATEPART(dw, '2023-03-08')), '2023-03-08') = '2023-03-12' (Sunday)

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