SQL - サブクエリ(相関サブクエリ(exists 演算子))

初めてのSQL
Alan Beaulieu (著)

開発環境

• OS: OS X Lion - Apple
• データベース言語: SQL
• リレーショナルデータベース: MySQL

『初めてのSQL』(Alan Beaulieu 著、株式会社クイープ 翻訳、オライリー・ジャパン、2006年、ISBN4-8733-181-8) の9章(サブクエリ),　9.7(練習問題)9-2を解いてみる。

9-2.

SQL文(TextWrangler)

SELECT a.account_id, a.product_cd, a.cust_id, a.avail_balance
FROM account a
WHERE EXISTS (
SELECT 1
FROM product p
WHERE a.product_cd = p.product_cd AND
  p.product_type_cd = 'LOAN'
);

入出力結果(Terminal)

$ mysql -u lrngsql -p bank
Enter password: 
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A

Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 9
Server version: 5.5.24 MySQL Community Server (GPL)

Copyright (c) 2000, 2011, Oracle and/or its affiliates. All rights reserved.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

mysql> desc account;
+--------------------+----------------------------------+------+-----+---------+----------------+
| Field              | Type                             | Null | Key | Default | Extra          |
+--------------------+----------------------------------+------+-----+---------+----------------+
| account_id         | int(10) unsigned                 | NO   | PRI | NULL    | auto_increment |
| product_cd         | varchar(10)                      | NO   | MUL | NULL    |                |
| cust_id            | int(10) unsigned                 | NO   | MUL | NULL    |                |
| open_date          | date                             | NO   |     | NULL    |                |
| close_date         | date                             | YES  |     | NULL    |                |
| last_activity_date | date                             | YES  |     | NULL    |                |
| status             | enum('ACTIVE','CLOSED','FROZEN') | YES  |     | NULL    |                |
| open_branch_id     | smallint(5) unsigned             | YES  | MUL | NULL    |                |
| open_emp_id        | smallint(5) unsigned             | YES  | MUL | NULL    |                |
| avail_balance      | float(10,2)                      | YES  |     | NULL    |                |
| pending_balance    | float(10,2)                      | YES  |     | NULL    |                |
+--------------------+----------------------------------+------+-----+---------+----------------+
11 rows in set (0.03 sec)

mysql> desc product;
+-----------------+-------------+------+-----+---------+-------+
| Field           | Type        | Null | Key | Default | Extra |
+-----------------+-------------+------+-----+---------+-------+
| product_cd      | varchar(10) | NO   | PRI | NULL    |       |
| name            | varchar(50) | NO   |     | NULL    |       |
| product_type_cd | varchar(10) | NO   | MUL | NULL    |       |
| date_offered    | date        | YES  |     | NULL    |       |
| date_retired    | date        | YES  |     | NULL    |       |
+-----------------+-------------+------+-----+---------+-------+
5 rows in set (0.00 sec)

mysql> SELECT a.account_id, a.product_cd, a.cust_id, a.avail_balance
    -> FROM account a
    -> WHERE EXISTS (
    -> SELECT 1
    -> FROM product p
    -> WHERE a.product_cd = p.product_cd AND
    ->   p.product_type_cd = 'LOAN'
    -> );
+------------+------------+---------+---------------+
| account_id | product_cd | cust_id | avail_balance |
+------------+------------+---------+---------------+
|         25 | BUS        |      10 |          0.00 |
|         27 | BUS        |      11 |       9345.55 |
|         29 | SBL        |      13 |      50000.00 |
+------------+------------+---------+---------------+
3 rows in set (0.03 sec)

mysql> quit
Bye
$