Count joined table : Join Select « Join « SQL / MySQL






  1. SQL / MySQL
  2. Join
  3. Join Select

Count joined table

    
mysql>
mysql>
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 (0.00 sec)

mysql>
mysql>
mysql>
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>
mysql>
mysql> CREATE TABLE categories (
    ->   catID int(11) NOT NULL auto_increment PRIMARY KEY ,
    ->   catName varchar(60),
    ->   parentCatID int(11),
    ->   ts timestamp
    -> );
Query OK, 0 rows affected (0.00 sec)

mysql>
mysql>
mysql>
mysql> INSERT INTO categories VALUES (1,'Computer books',11,'2004-12-02 18:37:20'),
    ->                                 (2,'Databases',1,'2004-12-02 18:37:20'),
    ->                                 (3,'Programming',1,'2004-12-02 18:37:20'),
    ->                                 (4,'Relational Databases',2,'2004-12-02 18:37:20'),
    ->                                 (5,'Object-oriented databases',2,'2004-12-02 18:37:20'),
    ->                                 (6,'PHP',3,'2004-12-02 18:37:20'),
    ->                                 (7,'Perl',3,'2004-12-02 18:37:20'),
    ->                                 (8,'SQL',2,'2004-12-02 18:37:20'),
    ->                                 (9,'Children\'s books',11,'2004-12-02 18:37:20'),
    ->                                 (10,'Literature and fiction',11,'2004-12-02 18:37:20'),
    ->                                 (11,'All books',NULL,'2004-12-02 18:37:20');
Query OK, 11 rows affected (0.00 sec)
Records: 11  Duplicates: 0  Warnings: 0

mysql>
mysql>
mysql>
mysql> SELECT catName, COUNT(title) AS nrOfItems
    -> FROM categories LEFT JOIN titles ON titles.catid = categories.catid
    -> GROUP BY catname
    -> ORDER BY nrOfItems DESC;
+---------------------------+-----------+
| catName                   | nrOfItems |
+---------------------------+-----------+
| Databases                 |         1 |
| PHP                       |         1 |
| Programming               |         1 |
| All books                 |         0 |
| Relational Databases      |         0 |
| SQL                       |         0 |
| Computer books            |         0 |
| Object-oriented databases |         0 |
| Children's books          |         0 |
| Literature and fiction    |         0 |
| Perl                      |         0 |
+---------------------------+-----------+
11 rows in set (0.00 sec)

mysql>
mysql>
mysql> drop table titles;
Query OK, 0 rows affected (0.00 sec)

mysql> drop table categories;
Query OK, 0 rows affected (0.00 sec)

mysql>








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