如何在MySQL中连接多个表？

我想看看客户从给定的制造商订购什么。如何在MySQL中连接多个表？

我有论文表（含列）：

项目（item_num，order_num，stock_num，manu_code，数量等）
股票（stock_num，manu_code，描述，unit_price等）
订单（order_num，order_date，CUSTOMER_NUM，ship_instruct等）
客户（CUSTOMER_NUM，FNAME，LNAME，公司，地址1等）

这是我的查询的权利，但我相信这是返回一个跨某种产品：

SELECT concat(c.fname," ", c.lname) AS fullname, s.description 
FROM items i, stock s, customer c JOIN orders o 
ON o.customer_num=c.customer_num 
WHERE o.order_num=i.order_num AND i.manu_code = 'ANZ';

它会返回大量重复entires的大名单（1000线），

Anthony Higgens | baseball gloves 
Anthony Higgens | baseball gloves 
     .     . 
     .     . 
     .     . 
Kim Satifer  | running shoes

我在做什么错？

来源

2013-01-21 broinjc

尝试通过该项目的ID或任何你分组需要。 – Shomz

试试这个：

SELECT DISTINCT concat(c.fname," ", c.lname) AS fullname, s.description 
FROM customer c 
INNER JOIN orders o ON c.customer_num = o.customer_num 
INNER JOIN items i ON o.order_num = i.order_num 
INNER JOIN stock s on s.stock_num = i.stock_num 
WHERE i.manu_code = 'ANZ'

来源

2013-01-21 18:32:15 Marco

这会返回太多的行。我只注意到物品和库存都有一个stock_num字段，并将最后一个INNER JOIN更改为：INNER JOIN stock s on s.stock_num = i.stock_num – broinjc

SELECT DISTINCT concat（c.fname，“”，c.lname）作为全名， s.description FROM customer c INNER JOIN订单o ON c.customer_num = o。customer_num INNER JOIN items i ON o.order_num = i.order_num INNER JOIN股票s on.stock_num = i.stock_num WHERE i.manu_code ='ANZ'; – broinjc

@broinjc：是的，你是对的...我没有注意到那个领域...谢谢 – Marco

FROM items i, stock s, customer c确实参与了这三个表的笛卡尔连接，但您的WHERE对该笛卡尔连接做的限制很少。

如果你做了一些更明确的加入，你会明白减少重复，更正确地表达你正在做的事情。使用INNER JOINS和正确的连接标准，而不是仅列出FROM之后的所有表。例如：（还有更多这样的标准，您需要应用到JOINS，但这只是一个示例）：INNER JOIN stock ON stack.manu_code = items.manu_code。

最后，您可以使用SELECT DISTINCT或GROUP BY来进一步减少重复。但是，如果您使用JOIN标准获得明确的JOIN，则不应该有太多重复项。

来源

2013-01-21 18:29:02 DWright

当我做一个GROUP BY全名时，它会显示客户订购了'ANZ'产品，但所有的描述都是'网球拍'。我如何连接他们订购的产品的描述？ – broinjc

尝试使用'GROUP_CONCAT'。 – DWright

这应该工作：

 

     SELECT   concat(a.fname, " ", a.lname) as name 
         , d.description as desc 
     FROM   CUSTOMER a 
     INNER JOIN  ORDERS  b 
      on   a.customer_num = b.customer_num 
     INNER JOIN  ITEMS  c 
      on   b.order_num = c.order_num 
     INNER JOIN  STOCK  d 
      on   c.manu_code = d.manu_code 
     where   c.manu_code like 'ANZ' 
     group by  name,desc

来源

2013-01-22 06:38:31

谢谢大家，我觉得这是现在的工作：

SELECT DISTINCT concat(c.fname," ", c.lname) AS fullname, s.description 
FROM customer c 
INNER JOIN orders o ON c.customer_num = o.customer_num 
INNER JOIN items i ON o.order_num = i.order_num 
INNER JOIN stock s on s.stock_num = i.stock_num 
WHERE i.manu_code = 'ANZ';

来源

2013-01-22 16:59:36 broinjc

如何在MySQL中连接多个表？

回答

相关问题