如何在 SQL Server 中将行合并为单行答案

【问题标题】：How to merge to rows into a single row in SQL Server如何在 SQL Server 中将行合并为单行
【发布时间】：2018-05-03 05:33:37
【问题描述】：

我有一个执行联合操作的查询。这是查询

SELECT R.ThanaID, R.RoadTypeId, Count(R.Id) AS NoRdExist, 0 AS NoRdImp, 0 AS 
BcLenExist, 0 AS BcLenImp FROM RoadInventory AS R 
        INNER JOIN Thana AS A ON R.ThanaID = A.Id GROUP BY R.ThanaID,R.RoadTypeId 

UNION SELECT R.ThanaID, R.RoadTypeId, 0 AS NoRdExist, Count(R.Id) AS 
NoRdImp,0 AS BcLenExist, 0 AS BcLenImp FROM RoadInventory_Temp AS R
        INNER JOIN Thana AS A ON R.ThanaID = A.Id GROUP BY R.ThanaID, R.RoadTypeId 

UNION SELECT R.ThanaID, RI.RoadTypeId, 0 AS NoRdExist, 0 AS NoRdImp, 
Sum(CASE WHEN(R.SurfaceType='BC') THEN ((R.ToChain-R.FromChain)/1000) END) 
AS BcLenExist, 0 AS BcLenImp
    FROM (RoadInventory AS RI 
        INNER JOIN Thana AS A ON RI.ThanaID = A.Id) 
        INNER JOIN Segment AS R ON (RI.Id = R.RoadID) AND (RI.ThanaID = R.ThanaID) GROUP BY R.ThanaID, RI.RoadTypeId 

UNION SELECT R.ThanaID, RI.RoadTypeId, 0 AS NoRdExist, 0 AS NoRdImp, 0 AS 
BcLenExist, Sum(CASE WHEN(R.SurfaceType='BC') THEN ((R.ToChain-R.FromChain)/1000) END) 
AS BcLenImp
    FROM (RoadInventory_Temp AS RI 
        INNER JOIN Thana AS A ON RI.ThanaID = A.Id) 
        INNER JOIN Segment_Temp AS R ON (RI.Id = R.RoadID) AND (RI.ThanaID = R.ThanaID) GROUP BY R.ThanaID, RI.RoadTypeId

结果是这样的

ThanaID |RoadTypeId |NoRdExist |NoRdImp |BcLenExist |BcLenImp |
...............................................................
10101   |2          |0         |0       |0          |92
...............................................................
10101   |2          |0         |0       |92         |0
............................................................... 
10101   |2          |0         |8       |0          |0
...............................................................
10101   |2          |8         |0       |0          |0
............................................................... 
10101   |3          |0         |0       |0          |42
...............................................................
10101   |3          |0         |0       |42         |0
...............................................................
10101   |3          |0         |26      |0          |0
...............................................................
10101   |3          |26        |0       |0          |0
...............................................................

现在我想将包含 0（零）的列合并到包含值的列中。像这样

ThanaID |RoadTypeId |NoRdExist |NoRdImp |BcLenExist |BcLenImp |
...............................................................
10101   |2          |8         |8       |92         |92
............................................................... 
10101   |3          |26        |26      |42         |42
...............................................................

我怎样才能挤压这些行？

【问题讨论】：

我不知道您的架构，但快速查看查询表明不需要联合。您也许可以在具有多个连接的单个查询中实现这一点。如果没有，请将此联合与另一个在所需列上使用 sum 函数的 select 包装起来。
简单地说，将当前查询包装为 CTE，然后通过 ThanaID 聚合，获取所有列的总和。或者，按照@danish 的建议，尝试编写一个查询来处理所有事情。
旁注：为什么UNION 而不是简单的UNION ALL？我不认为有任何重复要删除，是吗？那你为什么一直加入Thana 表？你没有使用它。

标签： sql sql-server union

【解决方案1】：

您希望每个 ThanaID 和 RoadTypeId 有一个结果行以及其他值的总和。因此，根据您的查询，您可以简单地聚合：

select thanaid, roadtypeid, sum(nordexist), sum(nordimp), sum(bclenexist), sum(bclenimp)
from ( your query here )
group by thanaid, roadtypeid
order by thanaid, roadtypeid;

（我可能会以不同的方式编写查询，以免在单独的行中获取值，但是对于上面给出的查询，现在查询是最简单的解决方案。）

【讨论】：

嗨。谢谢你的建议。您能分享一下您将如何编写此查询吗？我不能做 SUM，因为我有其他一些包含 VARCHAR 的列
那么您的描述和示例不完整。它不仅是零，也不是零和它们的总和，就像你的例子一样。对于字符串，您可能只是使用空值代替零（您也应该将其用于数值），因此您可以只使用MAX(value 或MIN(value)。无论如何，我已经发布了另一个完全避免联合中间结果的答案。

【解决方案2】：

您针对ThanaID 和RoadTypeId 运行不同的查询。然后通过UNION 组合它们。目前尚不清楚您为什么要这样做，因为您似乎对 UNION 结果不感兴趣。看来您想要一个合并的结果。可能是内连接，也可能是所有查询的完全外连接；我不知道。下面我展示了所有 ThanaID 和 RoadTypeId 组合的结果，从而避免了完全外连接，因为在 SQL Server 中，由于缺少 USING 子句，多个完全外连接相当笨拙。

select
  t.id as thanaid,
  rt.id as roadtypeid,
  q1.nordexist,
  q2.nordimp
from thana t
cross join roadtype rt
left join
(
  select thanaid, roadtypeid, count(*) as nordexist 
  from roadinventory 
  group by thanaid, roadtypeid 
) q1 on q1.thanaid = t.id and q1.roadtypeid = rt.id
left join
(
  select thanaid, roadtypeid, count(*) as nordimp
  from roadinventory_temp 
  group by thanaid, roadtypeid 
) q2 on q2.thanaid = t.id and q2.roadtypeid = rt.id
...

【讨论】：

【解决方案3】：

Hi group by ThanaID 和 RoadTypeID 然后对字段 NoRdExist,NoRdImp,BcLenExist 求和和 BcLenImp。试试这个

select  ThanaID ,RoadTypeId ,NoRdExist=sum(isnull(NoRdExist,0)),sum(isnull(NoRdImp,0) ) NoRdImp,sum(isnull(BcLenExist,0)  ) as BcLenExist,BcLenImp=sum(isnull(BcLenImp,0)   )  from (
SELECT R.ThanaID, R.RoadTypeId, Count(R.Id) AS NoRdExist, 0 AS NoRdImp, 0 AS 
BcLenExist, 0 AS BcLenImp FROM RoadInventory AS R 
        INNER JOIN Thana AS A ON R.ThanaID = A.Id GROUP BY R.ThanaID,R.RoadTypeId 

UNION SELECT R.ThanaID, R.RoadTypeId, 0 AS NoRdExist, Count(R.Id) AS 
NoRdImp,0 AS BcLenExist, 0 AS BcLenImp FROM RoadInventory_Temp AS R
        INNER JOIN Thana AS A ON R.ThanaID = A.Id GROUP BY R.ThanaID, R.RoadTypeId 

UNION SELECT R.ThanaID, RI.RoadTypeId, 0 AS NoRdExist, 0 AS NoRdImp, 
Sum(CASE WHEN(R.SurfaceType='BC') THEN ((R.ToChain-R.FromChain)/1000) END) 
AS BcLenExist, 0 AS BcLenImp
    FROM (RoadInventory AS RI 
        INNER JOIN Thana AS A ON RI.ThanaID = A.Id) 
        INNER JOIN Segment AS R ON (RI.Id = R.RoadID) AND (RI.ThanaID = R.ThanaID) GROUP BY R.ThanaID, RI.RoadTypeId 

UNION SELECT R.ThanaID, RI.RoadTypeId, 0 AS NoRdExist, 0 AS NoRdImp, 0 AS 
BcLenExist, Sum(CASE WHEN(R.SurfaceType='BC') THEN ((R.ToChain-R.FromChain)/1000) END) 
AS BcLenImp
    FROM (RoadInventory_Temp AS RI 
        INNER JOIN Thana AS A ON RI.ThanaID = A.Id) 
        INNER JOIN Segment_Temp AS R ON (RI.Id = R.RoadID) AND (RI.ThanaID = R.ThanaID) GROUP BY R.ThanaID, RI.RoadTypeId) as t
        group by ThanaID ,RoadTypeId

【讨论】：