How To Use Subqueries with the EXISTS Operator

Q

How To Use Subqueries with the EXISTS Operator? - MySQL FAQs - SQL SELECT Statements with JOIN and Subqueries

✍: FYIcenter.com

A

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)

2007-05-11, 6163👍, 0💬