mysql子查询中EXISTS用法的例子

mysql> CREATE TABLE titles (
    ->   titleID int(11),
    ->   title varchar(100),
    ->   subtitle varchar(100),
    ->   edition tinyint(4),
    ->   publID int(11),
    ->   catID int(11),
    ->   langID int(11),
    ->   year int(11),
    ->   isbn varchar(20),
    ->   comment varchar(255),
    ->   ts timestamp,
    ->   authors varchar(255),
    ->   PRIMARY KEY  (titleID)
    -> );
Query OK, 0 rows affected (0.01 sec)

mysql> INSERT INTO titles VALUES (1,'linux','Installation',5,1,57,2,2000,NULL,NULL,'2005-02-28 13:34:21','Michael'),
    ->                           (2,'Excel',NULL,NULL,2,3,NULL,2000,NULL,NULL,'2005-02-28 13:34:22','David'),
    ->                           (3,'XML',NULL,NULL,1,2,NULL,1997,NULL,NULL,'2005-02-28 13:34:22','Edwards'),
    ->                           (4,'PHP',NULL,NULL,3,6,NULL,2000,NULL,NULL,'2005-02-28 13:34:22','Tom'),
    ->                           (5,'MySQL','',0,3,34,NULL,2000,'','','2005-02-28 13:34:22','Paul'),
    ->                           (6,'Java',NULL,NULL,4,34,NULL,1999,NULL,NULL,'2005-02-28 13:34:22','Tim');
Query OK, 6 rows affected (0.00 sec)
Records: 6  Duplicates: 0  Warnings: 0

mysql> CREATE TABLE publishers (
    ->   publID int(11) NOT NULL auto_increment,
    ->   publName varchar(60) collate latin1_german1_ci NOT NULL default '',
    ->   ts timestamp NOT NULL default CURRENT_TIMESTAMP on update CURRENT_TIMESTAMP,
    ->   PRIMARY KEY  (publID),
    ->   KEY publName (publName)
    -> ) ENGINE=innodb DEFAULT CHARSET=latin1 COLLATE=latin1_german1_ci;
Query OK, 0 rows affected (0.00 sec)

mysql> INSERT INTO publishers VALUES (1,'A','2004-12-02 18:36:58'),
    ->                                 (2,'Apress','2004-12-02 18:36:58'),
    ->                                 (3,'New Riders','2004-12-02 18:36:58'),
    ->                                 (4,'O'Reilly & Associates','2004-12-02 18:36:58'),
    ->                                 (5,'Hanser','2004-12-02 18:36:58');
Query OK, 5 rows affected (0.00 sec)
Records: 5  Duplicates: 0  Warnings: 0

mysql> SELECT title FROM titles WHERE EXISTS --//exists的用法
    -> (SELECT * FROM publishers WHERE
    -> titles.publID = publishers.publID AND
    -> publName LIKE 'O%');
+-------+
| title |
+-------+
| Java  |
+-------+
1 row in set (0.00 sec)