如何解决sql中的case语句使用同一语句中的其他选定列
| 我想知道在SQL Server 2005中是否可以进行以下操作。列A和B是在我的实际存储过程中使用其他case语句计算的。我不想不必要地在其他字段重复相同的内容。如果这在语法上不可行,还有其他想法吗?SELECT A,B,CASE WHEN column1=\'1\' THEN A ELSE B END Col1.
根据要求提供的实际查询的修改版本。在这种模式下,CTE似乎很难。 WANNABE是我要在sub select语句中完成的列。
SELECT 1 AS Region,\'Test\',CAST(Work AS NUMERIC(18,2)) Work,Work + 2 AS Work2,WANNABE
FROM
(
SELECT
ROW_NUMBER() OVER(PARTITION BY G.Value,C.C,FR.Mod1 ORDER BY FR.Date DESC,FG.Date DESC,FC.Date DESC) ROW,CASE WHEN COALESCE(FR.Mod1,\'\') = \'\' THEN \'\' ELSE FR.Mod1 END Mod1,CASE WHEN @var1=1 AND @var2 = 1 THEN FR.Col1 * G.Value
WHEN @var1=1 AND @var2 = 0 THEN FP.Col1 * G.Value END Work,CASE WHEN 1=1 THEN Work ELSE 1 END WANNABE,(
SELECT Col3
FROM Table2
WHERE c = FR.Value
) AS Custom
FROM MainTable FR
JOIN @C C ON FR.Col2 = C.Col2
LEFT JOIN Function1(@VersionDate) cv ON cv.Code = C.Code
LEFT JOIN Function2(@VersionDate) hv ON hv.Code = C.Code
LEFT JOIN @G G ON 1 = 1
LEFT JOIN SubTable1 FG ON FG.Number = G.Value,2 AND FG.Date = @VersionDate
LEFT JOIN SubTable2 FO ON FO.Number = G.Value
AND FO.Date = @VersionDate AND FO.Code = FR.Code AND FR.Mod1 = FO.Mod1
LEFT JOIN SubTable3 FP ON FP.Code = FR.Code AND FP.VersionDate = @Versiondate
AND CASE WHEN DATALENGTH(FR.Mod1) = 0 THEN \'00\' ELSE FR.Mod1 END = CASE WHEN DATALENGTH(FP.Mod1) = 0 THEN \'00\' ELSE FP.Mod1 END
LEFT JOIN SubTable4 FC ON FC.Date = @VersionDate
WHERE FR.Date = @VersionDate
) x
WHERE x.Row = 1
AND RTRIM(LTRIM(x.Col1)) IN (\'\',\'2\')
解决方法
您可以在CTE中定义“ 2”列别名,然后在外部选择中引用它们。
;WITH CTE AS
(
SELECT CASE ... END AS A,CASE ... END AS B,column1
FROM your_table
)
SELECT A,B,CASE WHEN column1=\'1\' THEN A ELSE B END Col1
FROM CTE
同样,您也可以用ѭ4define定义它们,有时会有些冗长。
一个仅显示语法的愚蠢示例是
SELECT A,CASE WHEN type=\'P\' THEN A ELSE B END Col1
FROM master..spt_values
CROSS APPLY (SELECT CASE WHEN number %2 = 1 THEN 1 END,CASE WHEN number %2 = 0 THEN 0 END) T(A,B)
更新之后,您可以将派生表替换为CTE并嵌套CTE,如下所示
;WITH x as
(
SELECT
ROW_NUMBER() OVER(PARTITION BY G.Value,C.Code,FR.Mod1 ORDER BY FR.Date DESC,FG.Date DESC,FC.Date DESC) ROW,...<snip>
WHERE FR.Date = @VersionDate
),x2 As
(
SELECT *,CASE WHEN 1=1 THEN Work ELSE 1 END WANNABE
FROM x
)
SELECT 1 AS Region,\'Test\',CAST(Work AS NUMERIC(18,2)) Work,Work + 2 AS Work2,WANNABE
FROM x2
WHERE x2.Row = 1
AND RTRIM(LTRIM(x2.Col1)) IN (\'\',\'2\')
,是的,这是可能的,但是您的所有sql语句如何?您可以在使用时在select语句中使用case语句。
像这样
SELECT SUM((CASE WHEN column1=\'1\' THEN 10 ELSE 0 END)) AS A,SUM((CASE WHEN column1=\'2\' THEN 10 ELSE 0 END)) AS B
FROM YourTable
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