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SQL Server FAQ - Using Group Functions in the SELECT Clause

By: FYIcenter.com

(Continued from previous topic...)

How To Use Group Functions in the SELECT Clause?

If group functions are used in the SELECT clause, all rows that meet the criteria defined in the WHERE clause will be treated as a single group. The group functions will be apply all rows in that group as a whole. The final output of the SELECT statement is the resulting values of the group functions, not the rows in the group.

Here are two good examples of using group functions :

SELECT COUNT(*), MAX(counts), MIN(created) 
   FROM fyi_links
COUNT(*) MAX(counts)  MIN(created)
7        972          2003-01-01

SELECT COUNT(*), MAX(counts), MIN(created) 
   FROM fyi_links WHERE tag = 'DBA'
COUNT(*) MAX(counts)  MIN(created)
3        972          2005-01-01

In first case, the group contains all the rows in table fyi_links, because is no WHERE clause. In the second case, the group contains only 3 rows because of the WHERE clause tag = 'DBA'.

(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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