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SQL Server FAQ - Using Multiple Columns in the GROUP BY Clause

By: FYIcenter.com

(Continued from previous topic...)

Can Multiple Columns Be Used in GROUP BY?

If you want to break your output into smaller groups, you can specify multiple column names or expressions in the GROUP BY clause. Output in each group must satisfy a specific combination of the expressions listed in the GROUP BY clause. The more columns or expressions entered in the GROUP BY clause, the smaller the groups will be.

The tutorial exercise below shows you how to break data into groups per "tag" and per year when they were created. Then the group function COUNT(*) is applied on each group:

SELECT tag, YEAR(created), COUNT(*) 
   FROM fyi_links GROUP BY tag, YEAR(created)
GO
tag     year(created)   count(*)
SQA     2003            1
DEV     2004            1
DBA     2005            1
DBA     2006            1
DEV     2006            1
DBA     2007            1
SQA     2007            1

So there is only one row in each group.

(Continued on next topic...)

  1. What Is a SELECT Query Statement?
  2. How To Create a Testing Table with Test Data?
  3. How To Select All Columns of All Rows from a Table with a SELECT statement?
  4. How To Select Some Specific Columns from a Table in a Query?
  5. How To Select Some Specific Rows from a Table?
  6. How To Add More Data to the Testing Table?
  7. How To Sort the Query Output with ORDER BY Clauses?
  8. Can the Query Output Be Sorted by Multiple Columns?
  9. How To Sort Query Output in Descending Order?
  10. How To Count Rows with the COUNT(*) Function?
  11. Can SELECT Statements Be Used on Views?
  12. How To Filter Out Duplications in the Returning Rows?
  13. What Are Group Functions in Query Statements?
  14. How To Use Group Functions in the SELECT Clause?
  15. Can Group Functions Be Mixed with Non-group Selection Fields?
  16. How To Divide Query Output into Multiple Groups with the GROUP BY Clause?
  17. How To Apply Filtering Criteria at Group Level with The HAVING Clause?
  18. How To Count Duplicated Values in a Column?
  19. Can Multiple Columns Be Used in GROUP BY?
  20. Can Group Functions Be Used in the ORDER BY Clause?

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