How to determine weekday name from date in SQL Server

Data and Databases
1

I’m working with SQL Server and need to figure out how to get the weekday name from a specific date. For example, if I have a date like 2009-01-01, I want to know if it was a Wednesday, Thursday, or whatever day it actually was.

I’ve been searching around but I’m not sure what the best approach is. Does SQL Server have any built-in functions that can help me convert a date into the corresponding day name? Or would I need to create some kind of lookup table to map dates to weekdays?

Any help would be appreciated since I’m still learning SQL Server and date functions.

2

interesting question! have you tried the DATENAME function? what format do you need - full weekday names or abbreviated? and are you working with different time zones or just local dates?

3

totally agree! DATENAME is super handy. i just did SELECT DATENAME(weekday, '2009-01-01') as well, and it gave me ‘Thursday’ too. saves time for sure, no need for extra tables!

4

The Problem:

You need to retrieve the weekday name (e.g., Monday, Tuesday) corresponding to a specific date in SQL Server. You’re unsure of the best approach, considering built-in functions or the creation of a lookup table.

TL;DR: The Quick Fix:

Use the DATENAME function. For example: SELECT DATENAME(weekday, '2009-01-01'); This will return ‘Thursday’. For abbreviated weekday names, use FORMAT: SELECT FORMAT('2009-01-01', 'ddd'); which returns ‘Thu’.

:thinking: Understanding the “Why” (The Root Cause):

SQL Server provides built-in functions specifically designed for date and time manipulation. Creating a lookup table would be inefficient and unnecessary for this task. The DATENAME function directly extracts the day name from a given date, handling complexities like leap years automatically. The FORMAT function offers more control over the output format.

:gear: Step-by-Step Guide:

  1. Use the DATENAME function: This is the most straightforward method. The syntax is: DATENAME (weekday, date). Replace date with your date value (e.g., a column name or a literal date string). This returns the full weekday name (e.g., ‘Monday’, ‘Tuesday’).

    SELECT DATENAME(weekday, '2024-03-08'); -- Returns 'Friday'
SELECT DATENAME(weekday, GETDATE()); -- Returns the weekday name for the current date.

  2. Use the FORMAT function (for abbreviated names): If you only need the abbreviated weekday name (e.g., ‘Mon’, ‘Tue’), use the FORMAT function: FORMAT (date, 'ddd'). Again, replace date with your date value.

    SELECT FORMAT('2024-03-08', 'ddd'); -- Returns 'Fri'
SELECT FORMAT(GETDATE(), 'ddd'); -- Returns the abbreviated weekday name for the current date.

  3. Handle NULL values (Optional): If your date column might contain NULL values, you should handle them to prevent errors. You can use ISNULL or COALESCE to provide a default value or a message for NULL dates:

    SELECT ISNULL(DATENAME(weekday, YourDateColumn), 'N/A') AS DayName FROM YourTable;

:mag: Common Pitfalls & What to Check Next:

  • Date Data Type: Ensure your date column is of the correct data type (DATE, DATETIME, DATETIME2). Incorrect data types can lead to unexpected results or errors.
  • Date Format: If you’re providing a date string, make sure it’s in a format that SQL Server understands (e.g., ‘YYYY-MM-DD’). Incorrect date formats can lead to conversion errors.
  • Time Zone Considerations: If you are working with dates and times across different time zones, carefully consider how time zone offsets might affect your results. GETDATE() returns the server’s local time. If your application and database servers are in different time zones, ensure your dates are correctly handled and adjusted.

:speech_balloon: Still running into issues? Share your (sanitized) table schema, sample data, the exact query you ran, and any error messages you received. The community is here to help!