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MySQL Tutorial - Using Subqueries with the EXISTS Operator

By: FYIcenter.com

(Continued from previous topic...)

How To Use Subqueries with the EXISTS Operator?

A subquery can be used with the EXISTS operator as "EXISTS (subquery)", which returns true if the subquery returns one or more rows. The following statement is a good example of "EXISTS (subquery)". It returns rows from fyi_links table that there are rows existing in the fyi_rates table with the same id.

mysql> SELECT id, url, tag, YEAR(created) As year 
   FROM fyi_links WHERE EXISTS (
   SELECT * FROM fyi_rates 
   WHERE fyi_rates.id = fyi_links.id);
+-----+-------------------+------+------+
| id  | url               | tag  | year |
+-----+-------------------+------+------+
| 101 | dev.fyicenter.com | DEV  | 2006 |
| 102 | dba.fyicenter.com | DBA  | 2006 |
| 103 | sqa.fyicenter.com | SQA  | 2006 |
+-----+-------------------+------+------+
3 rows in set (0.00 sec)

(Continued on next topic...)

  1. How To Join Two Tables in a Single Query?
  2. How To Write a Query with an Inner Join?
  3. How To Define and Use Table Alias Names?
  4. How To Write a Query with a Left Outer Join?
  5. How To Write a Query with a Right Outer Join?
  6. How To Write a Query with a Full Outer Join?
  7. How To Write an Inner Join with the WHERE Clause?
  8. How To Name Query Output Columns?
  9. What Is a Subquery?
  10. How To Use Subqueries with the IN Operator?
  11. How To Use Subqueries with the EXISTS Operator?
  12. How To Use Subqueries in the FROM clause?
  13. How To Count Groups Returned with the GROUP BY Clause?
  14. How To Return Top 5 Rows?
  15. How To Return the Second 5 Rows?
  16. How To Use UNION to Merge Outputs from Two Queries Together?

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