DATEPART and DATENAME in SQL Server

DATEPART pulls a number out of a date (month = 10). DATENAME pulls a word (October). Weekday numbers depend on DATEFIRST, which is not the same on every server.

Month and weekday

SELECT order_id, order_date,
       DATEPART(month, order_date) AS month_no,
       DATENAME(month, order_date) AS month_name,
       DATENAME(weekday, order_date) AS weekday_name
FROM Orders;

For “Monday to Sunday last week”, do not trust DATEPART(weekday, …) alone. Pin the week as on last week’s orders.