構造の変更に合わせたデータベースの更新

SQL リレーショナルデータベース入門

Timo Grossenbacher

Data Journalist

現在のデータベースモデル

新しいテーブルに重複のないデータのみを保存 DISTINCT

SELECT COUNT(*)
FROM university_professors;

 count
 -----
 1377

SELECT COUNT(DISTINCT organization) 
FROM university_professors;

 count
 -----
 1287

重複のないレコードを新しいテーブルに挿入INSERT DISTINCT INTO

INSERT INTO organizations 
SELECT DISTINCT organization, 
    organization_sector
FROM university_professors;

Output: INSERT 0 1287

INSERT INTO organizations 
SELECT organization, 
    organization_sector
FROM university_professors;

Output: INSERT 0 1377

INSERT INTO 文

INSERT INTO table_name (column_a, column_b)
VALUES ("value_a", "value_b");

affiliationsの列名を変更 RENAME COLUMN

CREATE TABLE affiliations (
 firstname text,
 lastname text,
 university_shortname text,
 function text,
 organisation text
);

ALTER TABLE table_name
RENAME COLUMN old_name TO new_name;

affiliationsの列を削除 DROP COLUMN

CREATE TABLE affiliations (
 firstname text,
 lastname text,
 university_shortname text,
 function text,
 organization text
);

ALTER TABLE table_name
DROP COLUMN column_name;

SELECT DISTINCT firstname, lastname, 
    university_shortname 
FROM university_professors
ORDER BY lastname;

-[ RECORD 1 ]--------+-------------
firstname            | Karl
lastname             | Aberer
university_shortname | EPF
-[ RECORD 2 ]--------+-------------
firstname            | Reza Shokrollah
lastname             | Abhari
university_shortname | ETH
-[ RECORD 3 ]--------+-------------
firstname            | Georges
lastname             | Abou Jaoudé
university_shortname | EPF
(truncated)

(551 records)

SELECT DISTINCT firstname, lastname 
FROM university_professors
ORDER BY lastname;

-[ RECORD 1 ]----------------------
firstname | Karl
lastname  | Aberer
-[ RECORD 2 ]----------------------
firstname | Reza Shokrollah
lastname  | Abhari
-[ RECORD 3 ]----------------------
firstname | Georges
lastname  | Abou Jaoudé
(truncated)

(551 records)

教授はfirstname と lastname のみで一意に識別される

やってみましょう！

SQL リレーショナルデータベース入門