Question

我需要创建HEADER和TRAILER记录。 TRAILER需要包括“主要”查询的行数。如何获取查询的@@ Rowcount并将其保存到variable中，以包含在TRAILER中。

看到这个。

--- Var to save Count

declare @cnt int

-- HEADER RECORD
Select Cast('H' as Char(2)) +
    Cast('MyFile' as Char(30))
    + CONVERT(Char(8),GetDate(),112)

union all

-- MAIN Query that I need the Count of

Select top 10 lastname from CUSTOMERS

set @cnt = @@ROWCOUNT

union all    <--ERROR obviously

-- TRAILER record  
Select Cast('T' as Char(2)) +
         CONVERT(Char(9),GetDate(),112) +
      Right(Replicate('0',9) + Cast(@cnt as VarChar(9)),9)

提前

Answer 1

您可以使用CTE重用主查询的定义：

WITH Query AS (
    SELECT top 10 lastname from CUSTOMERS
)
SELECT X.Result
FROM (
    SELECT Cast('H' as Char(2)) + Cast('MyFile' as Char(30)) 
        + CONVERT(Char(8),GetDate(),112) AS Result, 1 AS Position
    UNION ALL
    SELECT *, 2 AS Position FROM Query
    UNION ALL
    Select Cast('T' as Char(2)) + CONVERT(Char(9),GetDate(),112) + Right(Replicate('0',9) 
        + Cast((SELECT COUNT(*) FROM Query) as VarChar(9)),9) AS Result, 3 AS Position
) X ORDER BY X.Position

但是，CTE将被评估两次；如果查询复杂且耗时，则可能需要使用临时表：

SELECT TOP 10 lastname INTO #Temp FROM CUSTOMERS

SELECT X.Result
FROM (
    SELECT Cast('H' as Char(2)) + Cast('MyFile' as Char(30))
         + CONVERT(Char(8),GetDate(),112) AS Result, 1 AS Position
    UNION ALL
    SELECT *, 2 AS Position FROM #Temp
    UNION ALL
    Select Cast('T' as Char(2)) + CONVERT(Char(9),GetDate(),112) + Right(Replicate('0',9) 
         + Cast((SELECT COUNT(*) FROM #Temp) as VarChar(9)),9) AS Result, 3 AS Position
) X ORDER BY X.Position

Answer 2

尝试以下脚本-

-- HEADER RECORD
SELECT CAST('H' AS CHAR(2)) + CAST('MyFile' AS CHAR(30)) + CONVERT(CHAR(8), GETDATE(), 112)

UNION ALL

-- MAIN Query that I need the Count of
SELECT lastname FROM CUSTOMERS

UNION ALL

-- TRAILER record  
SELECT CAST('T' AS CHAR(2)) + CONVERT(CHAR(9), GETDATE(), 112) + RIGHT(REPLICATE('0', 9) + CAST(
(
    SELECT COUNT(lastname) FROM CUSTOMERS
) AS VARCHAR(9)), 9);

如何从UNION中的单个查询获取@@ ROWCOUNT-使用RowCount创建Trailer记录

2 个答案: