更改数据库结构：需要一个SQL查询

Question

我有两个表：

connections 
id | publisherId | authorId 

和

books 
id | connectionId | title 

我想合并这些表只得到一个表：

books 
id| publisherId | authorId | title 

我怎样才能做到这一点只有一个SQL查询？

Answer 1

CREATE TABLE newtable 
SELECT b.id, c.publisherId, c.authorID, b.title 
FROM books b 
INNER JOIN connections c 
on c.id = b.connectionId 

未经测试，但应该这样做。我假设你想要书籍表中的ID，否则你需要c.id而不是b.id.

然后您可以删除旧表并将其重命名为任何您想要的。

Answer 2

CREATE TABLE connections_books 
SELECT books.id as id, 
     connections.publisherId as publisherId, 
     connections.authorId as authorId, 
     books.title as title 
FROM books join connections on books.connectionId = connections.id; 

测试第一只使用select部分查询：

SELECT books.id as id, 
     connections.publisherId as publisherId, 
     connections.authorId as authorId, 
     books.title as title 
FROM books join connections on books.connectionId = connections.id; 

一旦给你你想要的，继续创建表的内容。

确保新表格中的列名是正确的是很重要的。使用select语句测试来确保您的列名是您想要的。如果要更改列名称，请更改所选每列的as ...名称。