SQL - クエリ入門(重複の削除(DISTINCT))

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、ISBN4-87311-281-8) の3章(クエリ入門),　3.8(練習問題)3-3.を解いてみる。

入出力結果(Terminal)

$ mysql -u lrngsql -p
Enter password: 
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 3
Server version: 5.5.18 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> show databases
    -> ;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| bank               |
| mysql              |
| performance_schema |
| sample_store       |
| store              |
| test               |
+--------------------+
7 rows in set (0.06 sec)

mysql> use bank;
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A

Database changed
mysql> show tables;
+----------------+
| Tables_in_bank |
+----------------+
| account        |
| branch         |
| business       |
| customer       |
| department     |
| employee       |
| favorite_food  |
| individual     |
| officer        |
| person         |
| product        |
| product_type   |
| transaction    |
+----------------+
13 rows in set (0.00 sec)

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 (0.71 sec)

mysql> select distinct open_emp_id from account;
+-------------+
| open_emp_id |
+-------------+
|           1 |
|          10 |
|          13 |
|          16 |
+-------------+
4 rows in set (0.23 sec)

mysql> quit;
Bye
$

今日も超スローペース。