如何使用 UNION 查询将相似项目合二为一

Question

当我使用 UNION 加入时，我目前在 2 个地方获得了类似的物品。

我想要的是它应该总结并显示相似项目的单个项目。

这是我的查询

select 
(Case 
When DHB = 'ABC.com' Then 'ABC Hospital'
When DHB = 'AOC.com' Then 'ABC Hospital'
When DHB = 'coe.com' Then 'EFG Hospital'
End) DHB
, count(*) NumberOfActiveUsers from (
select distinct Ltrim(Rtrim(substring(userid, charIndex('@', userId)+1, Len(userId)))) as DHB, userId from [RecordDB].[dbo].Event ae
where userId like '%@%'
) as Temp
where DHB in ('ABC.com','AOC.com','coe.com')
group by DHB

UNION

select distinct DHB,
 count(userid) NumberOfActiveUsers from (
SELECT DISTINCT userid,
CASE WHEN DHB in ('2.1','ABC001') THEN 'ABC Hospital'
     WHEN DHB in ('3.1','CDE001') THEN 'EFG Hospital'  
ELSE DHB END 
FROM 
(
SELECT 
    userid, 
    CASE 
       WHEN CHARINDEX('-', e.name) > 0 
          THEN Ltrim(Rtrim(substring(e.name,0, charIndex('-', e.name)))) 
       ELSE e.name 
    END as DHB      
FROM
    [RecordDB].[dbo].Event ae
JOIN
    [Portal].[dbo].cUser cu ON cu.name = ae.userID
JOIN
    [Portal].[dbo].UAttribute ua ON ua.cUser = cu.uniqueId
JOIN
    [Portal].[dbo].[EIdentifier] ei ON ei.cUser = cu.uniqueId
JOIN
    [Portal].[dbo].[EIdentifierType] e ON e.uniqueId = ei.externalIdentifierType
WHERE
    (e.name LIKE '%ABC001%' OR e.name LIKE '2.1' or e.name LIKE '%CDE001%' OR e.name LIKE '3.1')   
) as aa
)as Temp2
group by DHB

输出

DHB            NumberOfActiveUsers
ABC Hospital           2
ABC Hospital           5
EFG Hospital           3
EFG Hospital           8

预期的输出应该是

DHB            NumberOfActiveUsers
 ABC Hospital          7
 EFG Hospital          11

Answer 1

快速而肮脏的解决方案：

select distinct * from (
  select * from part1
  union all
  select * from part2
) t;

（这是 cmets 中建议的 group by 的替代方案，这是另一种有效的，也许是等效的途径。）

编辑 1 正如 cmets 中所写，这种“快速而肮脏”的做事方式不起作用，因为 OP 需要聚合函数 SUM。按 DHB 分组，我相信这会起作用：

select DHB, SUM(NumberOfActiveUsers) as NumberOfActiveUsers
from (
      select /*your first statement*/ from part1
      union all
      select /*your second statement*/ from part2
) t;