3 个 SELECT 中的 2 个与 UNION 结合返回的行数答案

【问题标题】：Count of rows returned by 2 out of 3 SELECTs combined with UNION3 个 SELECT 中的 2 个与 UNION 结合返回的行数
【发布时间】：2011-08-11 20:45:38
【问题描述】：

我很难为这篇文章命名。

我们如何才能完成以下任务？

SELECT 'Body' AS LineType, ItemName, Quantity FROM TableX
UNION ALL
SELECT 'Body' AS LineType, ItemName, Quantity FROM TableY
UNION ALL
SELECT 'Trailer' AS LineType, null As ItemName, <count of the above two SELECTs>

结果应该是这样的：

LineType     ItemName     Qty
Body         Nut          19
Body         Bolt         25
Trailer      NULL         2

请帮忙；感谢 SOF 社区。

【问题讨论】：

标签： sql-server tsql select union-all

【解决方案1】：

尝试 CTE：

;WITH FirstQ AS 
(
    SELECT 'Body' AS LineType, ItemName, Quantity FROM TableX
), SecondQ AS 
(
    SELECT 'Body' AS LineType, ItemName, Quantity FROM TableY
)
SELECT * FROM FirstQ
UNION ALL SELECT * FROM SecondQ
UNION ALL
SELECT 'Trailer' AS LineType, null As ItemName, ((SELECT COUNT(*) FROM FirstQ) +(SELECT COUNT(*) FROM SecondQ)) AS Quantity

工作示例代码：

declare @TableX table (ItemName varchar(5), Quantity int)
INSERT @TableX VALUES ('aa',10)
INSERT @TableX VALUES ('bb',20)

declare @TableY table (ItemName varchar(5), Quantity int)
INSERT @TableX VALUES ('cc',30)

;WITH FirstQ AS 
(
    SELECT 'Body' AS LineType, ItemName, Quantity FROM @TableX
), SecondQ AS 
(
    SELECT 'Body' AS LineType, ItemName, Quantity FROM @TableY
)
SELECT * FROM FirstQ
UNION ALL SELECT * FROM SecondQ
UNION ALL
SELECT 'Trailer' AS LineType, null As ItemName, ((SELECT COUNT(*) FROM FirstQ) +(SELECT COUNT(*) FROM SecondQ)) AS Quantity

输出：

LineType ItemName Quantity
-------- -------- -----------
Body     aa       10
Body     bb       20
Body     cc       30
Trailer  NULL     3

(4 row(s) affected)

【讨论】：

这行得通。只要 SOF 允许，我就会将此标记为答案。感谢您的快速回复。

【解决方案2】：

declare @TableX table (ItemName varchar(10),Quantity int)
declare @TableY table (ItemName varchar(10),Quantity int)

insert @tableX VALUES('door',0)
insert @tableX VALUES('window',10)
insert @tableX VALUES('wheel',5)
insert @tableX VALUES('brake',7)
insert @tableX VALUES('handle',3)
insert @tableX VALUES('lamp',207)

insert @tableY VALUES('Ydoor',0)
insert @tableY VALUES('Ywindow',10)
insert @tableY VALUES('Ywheel',5)
insert @tableY VALUES('Ybrake',7)
insert @tableY VALUES('Yhandle',3)
insert @tableY VALUES('Ylamp',207)

SELECT 'Body' as LineType, ItemName, Sum(Quantity) qty, Count(*) [count] FROM
(
SELECT ItemName, Quantity FROM @TableX
UNION
SELECT ItemName, Quantity FROM @TableY
) u

GROUP BY ItemName WITH ROLLUP

【讨论】：

几个错误：需要删除多余的UNION ALL，需要删除GROUP BY中的as LineType。之后，你仍然会得到：Each GROUP BY expression must contain at least one column that is not an outer reference.
@KM -- 感谢您的校对。懒得测试了。请参阅修改后的答案。
漂亮在旁观者的眼中。您的版本不提供 LineType='Trailer' 的行，而是将该行生成为 LineType='Body'。我敢打赌，OP 需要“Trailer”值来进行某些处理，而拥有“Body”值将无法满足他们的需求。