问题描述

我正在尝试创建一个新表，该表将由来自三个现有表的选定数据组成.

I am trying to create a new table that will consist of selected data from three existing tables.

现有的三个表设置如下，我想要的结果在底部:

The three existing tables are set up as following, and my desired result is at the bottom:

people
id      last_name   first_name  email
1       Smith       Fred        Fred@..
2       Jones       Tom         Tom@..
3       Doe         Jane        Jane@..

taxonomy
id      taxonomy    
1       age
2       gender
3       height

details
id      person_id   detail_id   content
1       1           1           36
2       1           2           M
3       1           3           5'10"
4       2           1           29
5       2           2           M
6       2           3           6'3"
7       3           1           27
8       3           2           F
9       3           3           5'8"


New Table
id      last_name   first_name  email   age
1       Smith       Fred        Fred@.. 36
2       Jones       Tom         Tom@..  29
3       Doe         Jane        Jane@.. 27

预先感谢您的帮助！

推荐答案

你需要做一个3-way JOIN:

You need to do a 3-way JOIN:

CREATE TABLE new_table AS
SELECT p.*, d.content AS age
FROM people AS p
JOIN details AS d ON d.person_id = p.id
JOIN taxonomy AS t ON t.id = d.detail_id
WHERE t.taxonomy = 'age'

演示

或者如果您已经创建了表格，您可以这样做:

Or if you've already created the table, you can do:

INSERT INTO new_table (id, last_name, first_name, email, age)
SELECT p.id, p.last_name, p.first_name, p.email, d.content AS age
FROM people AS p
JOIN details AS d ON d.person_id = p.id
JOIN taxonomy AS t ON t.id = d.detail_id
WHERE t.taxonomy = 'age'

要获得多个属性，您必须为每个属性分别加入详细信息和分类表:

To get multiple attributes, you have to join with the details and taxonomy tables separately for each attribute:

CREATE TABLE new_table AS
SELECT p.*, d1.content AS age, d2.content AS gender, d3.content AS height
FROM people AS p
JOIN details AS d1 ON d1.person_id = p.id
JOIN taxonomy AS t1 ON t1.id = d1.detail_id
JOIN details AS d2 ON d2.person_id = p.id
JOIN taxonomy AS t2 ON t2.id = d2.detail_id
JOIN details AS d3 ON d3.person_id = p.id
JOIN taxonomy AS t3 ON t3.id = d3.detail_id
WHERE t1.taxonomy = 'age' AND t2.taxonomy = 'gender' AND t3.taxonomy = 'height'

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