select TOP (all)

Question

declare @t int
set @t = 10
if (o = \'mmm\') set @t = -1
select top(@t) * from table

What if I want generally it resulted with 10 rows, but rarely a

Answer 1

a dynamic sql version isn't that's hard to do.

CREATE PROCEDURE [dbo].[VariableTopSelect] 
    -- Add the parameters for the stored procedure here
    @t int

AS
BEGIN
    -- SET NOCOUNT ON added to prevent extra result sets from
    -- interfering with SELECT statements.
    SET NOCOUNT ON;

declare @sql nvarchar(max)

if (@t=10)
begin
    set @sql='select top (10) * from table'
end
else
begin
    set @sql='select * from  table'
end

exec sp_executesql @sql


END

with this sp, if they send 10 to the sp, it'll select the top 10, otherwise it'll select all.

Answer 2

The best solution I've found is to select the needed columns with all of your conditions into a temporary table, then do your conditional top:

DECLARE @TempTable TABLE(cols...)

INSERT INTO @TempTable
SELECT blah FROM ...

if (condition)
 SELECT TOP 10 * FROM @tempTable
else
 SELECT * FROM @tempTable

This way you follow DRY, get your conditional TOP, and are just as easy to read.

Cheers.