SQL - 複数テーブルからのデータの取得(自己結合(等結合))

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5章(複数テーブルからのデータの取得),　5.6(練習問題)5-3を解いてみる。

5-3.

SQL文(TextWrangler)

select e.emp_id, e.fname, e.lname
from employee e inner join employee e_mgr
on e.superior_emp_id = e_mgr.emp_id
where e.dept_id != e_mgr.dept_id;

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 7
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 employee;
+--------------------+----------------------+------+-----+---------+----------------+
| Field              | Type                 | Null | Key | Default | Extra          |
+--------------------+----------------------+------+-----+---------+----------------+
| emp_id             | smallint(5) unsigned | NO   | PRI | NULL    | auto_increment |
| fname              | varchar(20)          | NO   |     | NULL    |                |
| lname              | varchar(20)          | NO   |     | NULL    |                |
| start_date         | date                 | NO   |     | NULL    |                |
| end_date           | date                 | YES  |     | NULL    |                |
| superior_emp_id    | smallint(5) unsigned | YES  | MUL | NULL    |                |
| dept_id            | smallint(5) unsigned | YES  | MUL | NULL    |                |
| title              | varchar(20)          | YES  |     | NULL    |                |
| assigned_branch_id | smallint(5) unsigned | YES  | MUL | NULL    |                |
+--------------------+----------------------+------+-----+---------+----------------+
9 rows in set (0.03 sec)

mysql> select e.emp_id, e.fname, e.lname
    -> from employee e inner join employee e_mgr
    -> on e.superior_emp_id = e_mgr.emp_id
    -> where e.dept_id != e_mgr.dept_id;
+--------+-------+-----------+
| emp_id | fname | lname     |
+--------+-------+-----------+
|      4 | Susan | Hawthorne |
|      5 | John  | Gooding   |
+--------+-------+-----------+
2 rows in set (0.00 sec)

mysql> quit;
Bye
$