Question

我正在尝试在SQL Server上执行以下查询：

DECLARE @Fid nvarchar(30) 
DECLARE @max nvarchar(30) 
DECLARE @min nvarchar(30) 
DECLARE @Value nvarchar(30) 

SET @Fid = '6'

SET @max = '317012' 
SET @min = '317061' 
SET @Value = 'ALL' 

IF(@Value = 'ALL') 
SELECT TOP 50 * FROM sample WHERE projectkey = 'Proj1'

IF(@Value = 'Next') 
SELECT TOP 50 * FROM sample WHERE msgid <= @min AND projectkey = 'Proj1'

IF(@Value = 'Previous') 
SELECT TOP 50 * FROM (SELECT TOP 50 * FROM sample WHERE projectkey = 'Proj1' AND msgid >= @max ORDER BY msgid ASC) as t ORDER BY msgid DESC

AND 

fid = (CASE WHEN @Fid = 'ALL' THEN fid WHEN @Fid = '' THEN fid ELSE @Fid END)

在上面的查询中，我试图根据if条件执行select子句，并根据select子句给出的结果我想在子句条件作为过滤器的情况下应用于结果。我试图避免在每个if块中重复过滤器（即where子句）。我们如何实现或修改上述查询来实现这样的输出？

Answer 1

试试这个

    SELECT TOP 50 * FROM sample WHERE projectkey = 'Proj1' and ((@Value = 'ALL')
    or (msgid <= @min  and @Value = 'Next')
    or (msgid >= @max and @Value = 'Previous'))

   order by 
   case when  @Value = 'Previous'
   then
   msgid 
   end 
   desc

如何根据条件和条件执行select子句在结果上应用多个过滤器？

1 个答案: