MYSQL从3个表中获取信息

Question

我有3个表格。第一个包含customer_group_id和account_number，将每个组链接到一个帐户。第二个包含customer_id和customer_group_id，将每个客户链接到一个客户组，第三个包含客户ID的客户描述。

我想获得该帐户中所有客户的customer_group的信息。我正在使用的语法如下：

SELECT *, CONCAT(c.firstname, ' ', c.lastname) AS name, cgd.name AS customer_group 
FROM customer c 
LEFT JOIN customer_group_description cgd 
LEFT JOIN customer_group cg 
ON (c.customer_group_id = cgd.customer_group_id) 
WHERE cg.account_number = '1' 

请任何帮助将不胜感激。

customer_group: 
-------------------------------------- 
| customer_group_id | account_number | 
-------------------------------------- 
| 1     | 1    | 
| 2     | 1    | 
| 3     | 1    | 
-------------------------------------- 

customer_group_description 
-------------------------------------- 
| customer_group_id | name   | 
-------------------------------------- 
| 1     | group1   | 
| 2     | group2   | 
| 3     | group3   | 
-------------------------------------- 

customer 
----------------------------------------------- 
| firstname | lastname | customer_group_id | 
----------------------------------------------- 
| john  | smith  | 1    | 
| black  | smith  | 1    | 
| gold  | smith  | 2    | 
| bob   | dylan  | 3    | 
----------------------------------------------- 

我希望这会有助于更好地阐明我的问题。这个想法是让所有在帐号1下的用户。

谢谢。

Answer 1

转到MySQL手册的UNION和UNION ALL读了这个问题：What is the difference between UNION and UNION ALL?