Question

我有一张表#months，如下所示

MONTH_ID    FISCAL_YEAR_MONTH   MIN_DATE    MAX_DATE
1               FSA201510       20151001    20151031
2               FSA201511       20151101    20151130
3               FSA201512       20151201    20151204

我使用下面的动态查询来更新表SCCount中的列mastercount（有3行） -

   DECLARE @SQL VARCHAR(8000),


   set @sql=
   'DECLARE @I INT,                    
             @ROWS INT,
             @fym varchar(6) 

   SET @ROWS=(SELECT count(*) from #MONTHS)      
   SET @I=1        
   WHILE @I<=@ROWS          
   BEGIN
    SET @fym=(SELECT RIGHT(FISCAL_YEAR_MONTH,6) from #MONTHS where month_id=@I)
    UPDATE mastercount 
    SET SCCount = (SELECT count(*) 
    FROM dw_extract.dbo.dw_fsa_'+cast(@fym as varchar(6))+'    
    )
    WHERE row=@I
    set @I=@I+1
    end'
   exec (@sql)

以上查询提供错误：Must declare the scalar variable "@fym".

Answer 1

你可以让UPDATE动态：

DECLARE @sql VARCHAR(8000), @fym varchar(6)

DECLARE @I INT, @ROWS INT

SET @ROWS=(SELECT count(*) from #MONTHS)      
SET @I=1    

WHILE @I<=@ROWS          
BEGIN
    SET @fym=(SELECT RIGHT(FISCAL_YEAR_MONTH,6) from #MONTHS where month_id=@I)

    SET @sql = 'UPDATE mastercount'
    SET @sql += ' SET SCCount = (SELECT count(*) '
    SET @sql += ' dw_extract.dbo.dw_fsa_' + cast(@fym as varchar(6))+ ') WHERE row=' + @I

    EXEC (@sql)

    SET @I=@I+1
END

Answer 2

这是使用计数表而不是循环执行此操作的另一种方法。如果你的循环真的只有三个，这将不会产生很大的不同。但是如果迭代次数增加，这将对性能产生巨大影响。

DECLARE @sql VARCHAR(max) = '';

WITH
    E1(N) AS (select 1 from (values (1),(1),(1),(1),(1),(1),(1),(1),(1),(1))dt(n)),
    E2(N) AS (SELECT 1 FROM E1 a, E1 b), --10E+2 or 100 rows
    cteTally(N) AS 
    (
        SELECT  ROW_NUMBER() OVER (ORDER BY (SELECT NULL)) FROM E2
    )

select @sql = @sql + 'UPDATE mastercount set SCCount = (select count(*) from dw_extract.dbo.dw_fsa_' 
    + (SELECT RIGHT(FISCAL_YEAR_MONTH,6) from #MONTHS where month_id = t.N)
    + ') WHERE row = ' + CAST(t.N as varchar(6)) + ';'
from cteTally t
where t.N < (SELECT count(*) from #MONTHS)

exec sp_executesql @sql

动态查询成功运行但不执行任何操作

2 个答案: