当结构变化时更新数据库

SQL 关系型数据库入门

Timo Grossenbacher

Data Journalist

当前的数据库模型

仅在新表中存储 DISTINCT 数据

SELECT COUNT(*)
FROM university_professors;

 计数
 -----
 1377

SELECT COUNT(DISTINCT organization) 
FROM university_professors;

 计数
 -----
 1287

将 DISTINCT 记录 INSERT 到新表中

INSERT INTO organizations 
SELECT DISTINCT organization, 
    organization_sector
FROM university_professors;

输出：INSERT 0 1287

INSERT INTO organizations 
SELECT organization, 
    organization_sector
FROM university_professors;

输出：INSERT 0 1377

INSERT INTO 语句

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

在 affiliations 中重命名列

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 中删除列

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;

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

（551 条记录）

SELECT DISTINCT firstname, lastname 
FROM university_professors
ORDER BY lastname;

-[ 记录 1 ]----------------------
firstname | Karl
lastname  | Aberer
-[ 记录 2 ]----------------------
firstname | Reza Shokrollah
lastname  | Abhari
-[ 记录 3 ]----------------------
firstname | Georges
lastname  | Abou Jaoudé
（已截断）

（551 条记录）

教授仅由 firstname、lastname 唯一标识

开始动手！

SQL 关系型数据库入门