将 MySQL 中的几列标准化为多对多 table

Question

我想将数据分布在多列中的 table 规范化为多对多 table。

在我的例子中，我有一个 person table 和 hobby1、hobby2、hobby3、hobby4 字符串列，其中包含在 hobby table 中找到的名称。有些是空的有些不是。

目前数据库设计如下：

目前 person_hobby 为空。

你能帮我用 SQL 查询填充 person_hobby table 与 [=21= 相关的 hobby 列中找到的所有字符串吗] 这样我以后就可以摆脱它们了？

谢谢

Answer 1

对每个爱好领域重复（注意 ON 子句中的 hobby1）：

INSERT IGNORE INTO person_hobby (person_id, hobby_id) 
     SELECT person.id, hobby.id
     FROM person
     INNER JOIN hobby ON (person.hobby1=hobby.name)

Answer 2

例如：

DROP TABLE IF EXISTS person;

CREATE TABLE person
(id INT NOT NULL AUTO_INCREMENT PRIMARY KEY
,name VARCHAR(12) NOT NULL
,hobby1 VARCHAR(15) NULL
,hobby2 VARCHAR(15) NULL
,hobby3 VARCHAR(15) NULL
,hobby4 VARCHAR(15) NULL
);

DROP TABLE IF EXISTS person_hobby;

CREATE TABLE person_hobby
(person_id INT NOT NULL 
,hobby_id INT NOT NULL
,PRIMARY KEY(person_id,hobby_id)
);

DROP TABLE IF EXISTS hobby;

CREATE TABLE hobby
(id INT NOT NULL AUTO_INCREMENT PRIMARY KEY
,name VARCHAR(15) NOT NULL UNIQUE
);

INSERT INTO person VALUES
(1,'John'  ,'Reading'   ,'Cycling','Swimming',NULL),
(2,'Paul'  ,'Travelling','TV','Bird watching','Cinema'),
(3,'George','Fishing'   ,'Swimming',NULL,NULL),
(4,'Ringo',NULL,NULL,NULL,NULL);

INSERT INTO hobby (name) 
SELECT hobby1 FROM person WHERE hobby1 IS NOT NULL UNION 
SELECT hobby2 FROM person WHERE hobby2 IS NOT NULL UNION 
SELECT hobby3 FROM person WHERE hobby3 IS NOT NULL UNION 
SELECT hobby4 FROM person WHERE hobby4 IS NOT NULL;

INSERT INTO person_hobby
SELECT p.id 
     , h.id 
  FROM
     (
SELECT id
     , hobby1 hobby
  FROM person
 UNION
SELECT id 
     , hobby2 
  FROM person
 UNION
SELECT id 
     , hobby3
  FROM person
 UNION
SELECT id 
     , hobby4
  FROM person
     ) p
  JOIN hobby h
    ON h.name = p.hobby;

Query OK, 9 rows affected (0.05 sec)
Records: 9  Duplicates: 0  Warnings: 0

SELECT * FROM person_hobby;
+-----------+----------+
| person_id | hobby_id |
+-----------+----------+
|         1 |        1 |
|         1 |        4 |
|         1 |        6 |
|         2 |        2 |
|         2 |        5 |
|         2 |        7 |
|         2 |        8 |
|         3 |        3 |
|         3 |        6 |
+-----------+----------+

现在删除 table 人的专栏。

将 MySQL 中的几列标准化为多对多 table

Normalize several columns to one many to many table in MySQL

mysql

database

many-to-many

relational-database