联合所有Sql查询-如何绑定三个表

我有以下表格：

T1

T2

T3

我想把它作为输出

ID  PRIORITY SERVICE/DEVICE
1      1        PSTN
1      1        ADSL
1      1        BSC1
2      1
3      2        ADSL
3      2        BSC7

如何使用UNIONALL绑定这些表？我还必须为T1

WHERE优先级设置WHERE子句=4

一个id的输出表中的总数应为T2+T3的汇总（对于id=12+1=3），但对于id=2，它也应存在于表输出中，第二列为空

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谢谢

如果您可以只使用

联合

而不使用

联合所有

这将满足您的需求

SELECT t1.Id, t1.Priority, COALESCE(t2.Service, '') AS [Service/Device]
FROM t1
LEFT JOIN t2 ON t1.Id = t2.Id
WHERE t1.Priority != 4

UNION 

SELECT t1.Id, t1.Priority, COALESCE(t3.Device, '') AS [Service/Device]
FROM t1
LEFT JOIN t3 ON t1.Id = t3.Id
WHERE t1.Priority != 4

---

如果您可以只使用

联合

而不使用

联合所有

这应该会满足您的需求

SELECT t1.Id, t1.Priority, COALESCE(t2.Service, '') AS [Service/Device]
FROM t1
LEFT JOIN t2 ON t1.Id = t2.Id
WHERE t1.Priority != 4

UNION 

SELECT t1.Id, t1.Priority, COALESCE(t3.Device, '') AS [Service/Device]
FROM t1
LEFT JOIN t3 ON t1.Id = t3.Id
WHERE t1.Priority != 4

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谢谢您的回复…我会很快尝试，但您确定我会得到重复的ID值，因为这是我想要的吗？对于ID 2，我会在服务/设备列中得到null或空白输出吗？Blank更合适，但我在Fiddle中看到有null？@Dejan我已经更新了我的答案，为您返回Blank而不是null。请让我知道这是否是您想要的输出谢谢回复…我会很快尝试，但您确定我会得到重复的ID值，因为这是我想要的吗？对于ID 2，我会在服务/设备列中得到null或空白输出吗？Blank更合适，但我在Fiddle中看到有null？@Dejan我已经更新了我的答案，为您返回Blank而不是null。请让我知道这是否是你想要的输出

ID  PRIORITY SERVICE/DEVICE
1      1        PSTN
1      1        ADSL
1      1        BSC1
2      1
3      2        ADSL
3      2        BSC7

SELECT t1.Id, t1.Priority, COALESCE(t2.Service, '') AS [Service/Device]
FROM t1
LEFT JOIN t2 ON t1.Id = t2.Id
WHERE t1.Priority != 4

UNION 

SELECT t1.Id, t1.Priority, COALESCE(t3.Device, '') AS [Service/Device]
FROM t1
LEFT JOIN t3 ON t1.Id = t3.Id
WHERE t1.Priority != 4

select T1.id , T1.PRIORITY ,T2.SERVICE  as service/Device from  t1 
left outer join T2 on T2.id=T1.id where T1.PRIORITY!=4
union all
select T1.id , T1.PRIORITY ,T3.DEVICE as service/Device from  t1 
left outer join T3 on T3.id=T1.id where PRIORITY!=4