SQL - サブクエリ(データソースとしてのサブクエリ、仮想テーブルの作成)

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)9-3を解いてみる。

9-3.

SQL文(TextWrangler)

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, '2003-12-31' 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;

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 1
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> show tables;
+----------------+
| Tables_in_bank |
+----------------+
| account        |
| branch         |
| business       |
| customer       |
| department     |
| employee       |
| individual     |
| officer        |
| product        |
| product_type   |
| tmp            |
| transaction    |
+----------------+
12 rows in set (0.03 sec)

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 (0.41 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, '2003-12-31' 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  |
|      2 | Susan    | Barker    | worker  |
|      3 | Robert   | Tyler     | mentor  |
|      4 | Susan    | Hawthorne | worker  |
|      5 | John     | Gooding   | worker  |
|      6 | Helen    | Fleming   | trainee |
|      7 | Chris    | Tucker    | trainee |
|      8 | Sarah    | Parker    | worker  |
|      9 | Jane     | Grossman  | worker  |
|     10 | Paula    | Roberts   | worker  |
|     11 | Thomas   | Ziegler   | mentor  |
|     12 | Samantha | Jameson   | worker  |
|     13 | John     | Blake     | mentor  |
|     14 | Cindy    | Mason     | worker  |
|     15 | Frank    | Portman   | worker  |
|     16 | Theresa  | Markham   | mentor  |
|     17 | Beth     | Fowler    | worker  |
|     18 | Rick     | Tulman    | worker  |
+--------+----------+-----------+---------+
18 rows in set (0.00 sec)

mysql> quit
Bye
$