MySQL从两个表中获取数据

Question

我在从两个表中获取我想要的结果时遇到问题

table #1: history

  customer_id  |  Action
 ------------------------
  217          |  buy
 ------------------------
  218          |  sell
 ------------------------
  219          |  hold
 ------------------------

 table #2: Customers

  customer_id    |  name
 ----------------------------
  217            |  Alan
 ----------------------------
  218            |  Jan
 ----------------------------
  219            |  Rick

我现在有一个很长的查询，但本质上我想添加以使名称与金额匹配。 我试过了，但是没有用：

(SELECT action AS action FROM "history` LEFT JOIN ON " customer(customer_id=customer_id)`)

我对查询不是很熟悉，因此不胜感激

Answer 1

应该是这样的：

SELECT h.Action AS action
   FROM history h
   LEFT JOIN Customers c
   ON h.customer_id = c.customer_id

您要么需要指定表，要么创建一个别名以与列/数据相关联。

Answer 2

是一个简单的连接

select action
from  history
left join Customers on Customers.Customer_id = history.customer_id

你可以确认使用

select history.customer_id, Customers.Customer_id history.action , Customers.name
from  history
left join Customers on Customers.Customer_id = history.customer_id

Answer 3

您可以像这样联接表：

SELECT history.action AS Action ,Customers.name AS Name
FROM `history`
LEFT JOIN `Customers` ON history.customer_id = Customers.customer_id;