Using the aggregate function in subquery : Introduction « Subquery « MySQL Tutorial

1. MySQL Tutorial
2. Subquery
3. Introduction

mysql>
mysql>
mysql> CREATE TABLE Books(
    ->    BookID SMALLINT NOT NULL PRIMARY KEY,
    ->    BookTitle VARCHAR(60) NOT NULL,
    ->    Copyright YEAR NOT NULL
    -> )
    -> ENGINE=INNODB;
Query OK, 0 rows affected (0.09 sec)

mysql>
mysql>
mysql> INSERT INTO Books VALUES (12786, 'Java',           1934),
    ->                          (13331, 'MySQL',          1919),
    ->                          (14356, 'PHP',            1966),
    ->                          (15729, 'PERL',           1932),
    ->                          (16284, 'Oracle',         1996),
    ->                          (17695, 'Pl/SQL',         1980),
    ->                          (19264, 'JavaScript',     1992),
    ->                          (19354, 'www.java2s.com', 1993);
Query OK, 8 rows affected (0.03 sec)
Records: 8  Duplicates: 0  Warnings: 0

mysql>
mysql>
mysql> CREATE TABLE Authors(
    ->    AuthID SMALLINT NOT NULL PRIMARY KEY,
    ->    AuthFN VARCHAR(20),
    ->    AuthMN VARCHAR(20),
    ->    AuthLN VARCHAR(20)
    -> )
    -> ENGINE=INNODB;
Query OK, 0 rows affected (0.05 sec)

mysql>
mysql>
mysql> INSERT INTO Authors VALUES (1006, 'H', 'S.', 'T'),
    ->                            (1007, 'J', 'C',  'O'),
    ->                            (1008, 'B', NULL, 'E'),
    ->                            (1009, 'R', 'M',  'R'),
    ->                            (1010, 'J', 'K',  'T'),
    ->                            (1011, 'J', 'G.', 'N'),
    ->                            (1012, 'A', NULL, 'P'),
    ->                            (1013, 'A', NULL, 'W'),
    ->                            (1014, 'N', NULL, 'A');
Query OK, 9 rows affected (0.03 sec)
Records: 9  Duplicates: 0  Warnings: 0

mysql>
mysql>
mysql> CREATE TABLE AuthorBook(
    ->    AuthID SMALLINT NOT NULL,
    ->    BookID SMALLINT NOT NULL,
    ->    PRIMARY KEY (AuthID, BookID),
    ->    FOREIGN KEY (AuthID) REFERENCES Authors (AuthID),
    ->    FOREIGN KEY (BookID) REFERENCES Books (BookID)
    -> )
    -> ENGINE=INNODB;
Query OK, 0 rows affected (0.36 sec)

mysql>
mysql>
mysql> INSERT INTO AuthorBook VALUES (1006, 14356),
    ->                               (1008, 15729),
    ->                               (1009, 12786),
    ->                               (1010, 17695),
    ->                               (1011, 15729),
    ->                               (1012, 19264),
    ->                               (1012, 19354),
    ->                               (1014, 16284);
Query OK, 8 rows affected (0.03 sec)
Records: 8  Duplicates: 0  Warnings: 0

mysql>
mysql>
mysql> select * from Authors;
+--------+--------+--------+--------+
| AuthID | AuthFN | AuthMN | AuthLN |
+--------+--------+--------+--------+
|   1006 | H      | S.     | T      |
|   1007 | J      | C      | O      |
|   1008 | B      | NULL   | E      |
|   1009 | R      | M      | R      |
|   1010 | J      | K      | T      |
|   1011 | J      | G.     | N      |
|   1012 | A      | NULL   | P      |
|   1013 | A      | NULL   | W      |
|   1014 | N      | NULL   | A      |
+--------+--------+--------+--------+
9 rows in set (0.00 sec)

mysql> select * from Books;
+--------+----------------+-----------+
| BookID | BookTitle      | Copyright |
+--------+----------------+-----------+
|  12786 | Java           |      1934 |
|  13331 | MySQL          |      1919 |
|  14356 | PHP            |      1966 |
|  15729 | PERL           |      1932 |
|  16284 | Oracle         |      1996 |
|  17695 | Pl/SQL         |      1980 |
|  19264 | JavaScript     |      1992 |
|  19354 | www.java2s.com |      1993 |
+--------+----------------+-----------+
8 rows in set (0.02 sec)

mysql> select * from AuthorBook;
+--------+--------+
| AuthID | BookID |
+--------+--------+
|   1009 |  12786 |
|   1006 |  14356 |
|   1008 |  15729 |
|   1011 |  15729 |
|   1014 |  16284 |
|   1010 |  17695 |
|   1012 |  19264 |
|   1012 |  19354 |
+--------+--------+
8 rows in set (0.00 sec)

mysql>
mysql>
mysql> SELECT BookTitle, Copyright
    -> FROM Books
    -> WHERE Copyright<(SELECT MAX(Copyright)-50 FROM Books)
    -> ORDER BY BookTitle;
+-----------+-----------+
| BookTitle | Copyright |
+-----------+-----------+
| Java      |      1934 |
| MySQL     |      1919 |
| PERL      |      1932 |
+-----------+-----------+
3 rows in set (0.00 sec)

mysql>
mysql> drop table AuthorBook;
Query OK, 0 rows affected (0.14 sec)

mysql> drop table Books;
Query OK, 0 rows affected (0.11 sec)

mysql> drop table Authors;
Query OK, 0 rows affected (0.03 sec)