Home >> FAQs/Tutorials >> MySQL Tutorials

MySQL Tutorial - Filerting out Duplications in Returning Rows

By: FYIcenter.com

(Continued from previous topic...)

How To Filter Out Duplications in Returning Rows?

If there are duplications in the returning rows, and you want to remove the duplications, you can use the keyword DISTINCT in the SELECT clause. The DISTINCT applies to the combination of all data fields specified in the SELECT clause. The tutorial exercise below shows you how DISTINCT works:

mysql> CREATE TABLE fyi_team (first_name VARCHAR(8), 
   last_name VARCHAR(8));

mysql> INSERT INTO fyi_team VALUES ('John', 'Gate');
mysql> INSERT INTO fyi_team VALUES ('John', 'Russell');
mysql> INSERT INTO fyi_team VALUES ('John', 'Seo');
mysql> INSERT INTO fyi_team VALUES ('John', 'Gate');
mysql> INSERT INTO fyi_team VALUES ('James', 'Gate');
mysql> INSERT INTO fyi_team VALUES ('Peter', 'Gate');
mysql> INSERT INTO fyi_team VALUES ('John', 'Gate');

mysql> SELECT * FROM fyi_team;
+------------+-----------+
| first_name | last_name |
+------------+-----------+
| John       | Gate      |
| John       | Russell   |
| John       | Seo       |
| John       | Gate      |
| James      | Gate      |
| Peter      | Gate      |
| John       | Gate      |
| John       | Gate      |
+------------+-----------+
8 rows in set (0.00 sec)

mysql> SELECT DISTINCT * FROM fyi_team;
+------------+-----------+
| first_name | last_name |
+------------+-----------+
| John       | Gate      |
| John       | Russell   |
| John       | Seo       |
| James      | Gate      |
| Peter      | Gate      |
+------------+-----------+
5 rows in set (0.00 sec)

mysql> SELECT DISTINCT last_name FROM fyi_team;
+-----------+
| last_name |
+-----------+
| Gate      |
| Russell   |
| Seo       |
+-----------+
3 rows in set (0.04 sec)

(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?

MySQL Tutorials:

More...


Other Tutorials/FAQs:

More...


Related Resources:

More...


Selected Jobs:

More...