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MySQL Tutorial - Group Functions with Non-group Selections

By: FYIcenter.com

(Continued from previous topic...)

Can Group Functions Be Mixed with Non-group Selection Fields?

If a group function is used in the SELECT clause, all other selection fields must be group level fields. Non-group fields can not be mixed with group fields in the SELECT clause. The script below gives you an example of invalid SELECT statements with group and non-group selection fields:

mysql> SELECT COUNT(*), url FROM fyi_links;
ERROR 1140 (42000): Mixing of GROUP columns 
   (MIN(),MAX(),COUNT(),...) with no GROUP columns
   is illegal if there is no GROUP BY clause

In this example, COUNT(*) is a group field and "url" is a non-group field.

(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?
4. How To Select Some Columns from a Table?
5. How To Select Some Rows from a Table?
6. How To Add More Data to the Testing Table?
7. How To Sort the Query Output?
8. Can the Query Output Be Sorted by Multiple Columns?
9. How To Sort Output in Descending Order?
10. How To Use SELECT Statement to Count Number of Rows?
11. Can SELECT Statements Be Used on Views?
12. How To Filter Out Duplications in Returning Rows?
13. What Are Group Functions?
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 Groups?
17. How To Apply Filtering Criteria at Group Level?
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?