Question

我想声明一个变量并执行以下操作：

Select     
cast (SUM(case when @Dummy is not null then 1 else 0 end)*1.0/443321 as decimal(10,5)) @Dummy    
FROM hellotable
WHERE @Dummy in ("100 different field names in hellotable")

然而这不起作用...感谢任何帮助。

Answer 1

尝试通过动态SQL实现..

DECLARE @dummy sysname
DECLARE @SQL NVARCHAR(MAX)

SELECT @SQL = 'SELECT  CAST (SUM(CASE WHEN '+ @Dummy +N' IS NOT NULL THEN 1
                       ELSE 0
                  END) * 1.0 / 443321 AS DECIMAL(10, 5)) '+ @Dummy +N'     
                FROM    hellotable
                WHERE   '+ @Dummy +N'  IN ( '' )'
EXEC (@SQL)

Answer 2

尝试使用临时表用数据填充这些表，然后使用主表用户内连接，而不是在WHERE子句中使用IN。

CREATE TABLE #TempTable (FieldFromHelloTable nvarchar(50))

INSERT INTO #TempTable
VALUES ('value1'),('value2'),('value3'),('value4'),('value5')

SELECT * --this is oversimplified to ilustrate the point and you can modify this further
FROM HelloTable H
inner join #TempTable Tmp on H.SomeField = Tmp.FieldFromHelloTable

SQL为长且重复的选择声明变量

2 个答案: