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MySQL Tutorial - Select Rows with WHERE Clause

By: FYIcenter.com

(Continued from previous topic...)

How To Select Some Rows from a Table?

If you don't want select all rows from a table, you can specify a WHERE clause to tell the query to return only the rows that meets the condition defined in the WHERE clause. The WHERE clause condition is a normal Boolean expression. If any data from table needs to be used in the Boolean expression, column names should be used to represent the table data.

The first select statement below only returns rows that have url names containing the letter "a". The second select statement returns no rows, because the WHERE clause results FALSE for all rows in the table.

mysql> SELECT * FROM fyi_links WHERE url LIKE '%a%';
| id  | url               | notes | counts | created       
| 102 | dba.fyicenter.com | NULL  |      0 | 2006-07-01 12:
| 103 | sqa.fyicenter.com | NULL  |   NULL | 2006-07-01 12:
2 rows in set (0.00 sec)

mysql> SELECT * FROM fyi_links WHERE FALSE;
Empty set (0.00 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?

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