結構變更時更新資料庫

SQL 關聯式資料庫入門

Timo Grossenbacher

Data Journalist

目前的資料庫模型

在新資料表只儲存 DISTINCT 資料

SELECT COUNT(*)
FROM university_professors;

 count
 -----
 1377

SELECT COUNT(DISTINCT organization) 
FROM university_professors;

 count
 -----
 1287

將 DISTINCT 記錄 INSERT INTO 新資料表

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 陳述式

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

在 affiliations 中重新命名欄位（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;

在 affiliations 中刪除欄位（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)

教授可由 firstname、lastname 唯一識別

開始動手吧！

SQL 關聯式資料庫入門