구조가 바뀔 때 데이터베이스 업데이트하기

SQL로 배우는 관계형 데이터베이스 입문

Timo Grossenbacher

Data Journalist

현재 데이터베이스 모델

새 테이블에는 DISTINCT 데이터만 저장

SELECT COUNT(*)
FROM university_professors;

 count
 -----
 1377

SELECT COUNT(DISTINCT organization) 
FROM university_professors;

 count
 -----
 1287

새 테이블에 DISTINCT 레코드 INSERT

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 문

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

affiliations에서 열 이름 변경(Rename)

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;

affiliations에서 열 삭제(DROP)

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)

교수는 firstname, lastname만으로 고유 식별됨

이제 시작합시다!

SQL로 배우는 관계형 데이터베이스 입문