Question

我试图获取数据库中所有用户的列表，但是当我运行以下查询时：

SELECT cu.user_name AS username, cu.display_name AS displayname, 
cm.lower_parent_name AS group, cu.email_address AS email
FROM cwd_user AS cu
INNER JOIN cwd_membership AS cm
ON cu.directory_id = cm.directory_id
AND cu.lower_user_name = cm.lower_child_name
AND cm.membership_type = 'GROUP_USER'
WHERE cm.lower_parent_name LIKE 'zz%'
ORDER BY cu.user_name;

我得到重复的条目（确定，因为我有同一个用户的多个值），但我只对小写的一个感兴趣。

+------------------------------------------------------------------+
|      username        |    displayname     |   group  |   email   |
+------------------------------------------------------------------+
|   firstname.lastname | Firstname Lastname | zz group | f.l@a.com |
|   Firstname.Lastname | Firstname Lastname | zz group | F.L@a.com |
+------------------------------------------------------------------+

我只想要其中一个用户（最好是第一个用户），所以我尝试了以下SQL查询：

SELECT t.user_name, cu.display_name, cm.lower_parent_name, 
cu.email_address
FROM (
SELECT cu.user_name
FROM cwd_user AS cu
INNER JOIN cwd_membership AS cm ON cu.directory_id=cm.directory_id
AND cu.lower_user_name=cm.lower_child_name
AND cm.membership_type='GROUP_USER'
WHERE cm.lower_parent_name LIKE 'zz%'
GROUP BY LOWER(cu.user_name) ) u JOIN cwd_user t ON t.user_name = 
u.user_name ORDER BY t.user_name;

但没有运气。我的SQL并不好，所以我被困在这里。

有什么想法吗？

Answer 1

您可以在子选择中选择适当的值并使用正确的别名引用，您应该使用distinct而不是group by

Person EffectiveDate  
123    1/1/2016  
123    2/1/2016  
123    4/1/2016  
123    5/1/2016  

Expected result would be  
123    3/1/2016

如果您只需要小写的user_name，则可以尝试二进制低级

SELECT  distinct 
        t.user_name
      , u.display_name
      , u.lower_parent_name
      , u.email_address
FROM (
  SELECT 
        cu.user_name
      , cu.display_name
      , cm.lower_parent_name
      , cu.email_address
  FROM cwd_user AS cu
  INNER JOIN cwd_membership AS cm  ON cu.directory_id=cm.directory_id
              AND cu.lower_user_name=cm.lower_child_name
              AND cm.membership_type='GROUP_USER'
  WHERE cm.lower_parent_name LIKE 'zz%'
) u 
JOIN cwd_user t ON t.user_name = u.user_name 
ORDER BY t.user_name;

Answer 2

SELECT distinct (t.user_name), cu.display_name, cm.lower_parent_name, 
cu.email_address
FROM (
SELECT cu.user_name
FROM cwd_user AS cu
INNER JOIN cwd_membership AS cm ON cu.directory_id=cm.directory_id
AND cu.lower_user_name=cm.lower_child_name
AND cm.membership_type='GROUP_USER'
WHERE cm.lower_parent_name LIKE 'zz%'
GROUP BY LOWER(cu.user_name) ) u JOIN cwd_user t ON t.user_name = 
u.user_name ORDER BY t.user_name;

在SQL SERVER中，DISTINCT关键字只选择不同的数据。

Answer 3

我最终在bash脚本中创建了两个单独的查询，这样就可以解决这个问题。

SQL获取没有重复的值（在不同情况下）

3 个答案: