SQL - サブクエリ(仮想テーブルの作成、内部結合(inner join))

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、ISBN4-87311-281-8) の9章(サブクエリ),　9.7(練習問題)9-3を解いてみる。

9-3.

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 (0.10 sec)

mysql> select e.emp_id,e.fname,e.lname,levels.name
    -> from employee e inner join (
    -> select 'trainee' name,'2004-01-01' start_dt,'2005-12-31' end_dt
    -> union all
    -> select 'worker' name,'2002-01-01' start_dt,'2003-13-31' end_dt
    -> union all
    -> select 'mentor' name,'2000-01-01' start_dt,'2001-12-31' end_dt ) levels
    -> on e.start_date between levels.start_dt and levels.end_dt;
+--------+---------+---------+---------+
| emp_id | fname   | lname   | name    |
+--------+---------+---------+---------+
|      1 | Michael | Smith   | mentor  |
|      3 | Robert  | Tyler   | mentor  |
|      6 | Helen   | Fleming | trainee |
|      7 | Chris   | Tucker  | trainee |
|     11 | Thomas  | Ziegler | mentor  |
|     13 | John    | Blake   | mentor  |
|     16 | Theresa | Markham | mentor  |
+--------+---------+---------+---------+
7 rows in set, 18 warnings (0.70 sec)

mysql> quit;
Bye
$