CREATE PROCEDURE pro_sample 
    @A varchar(8000),
    @B int,
    @C datetime
AS begin
    select * 
    from table
    where 1=1
    and (@A is null or a like @A+'%')
    and (@B is null or b = @B)
    and (@C is null or c = @C)
    order by a,b,c
end
GO 

CREATE PROCEDURE pro_sample 
    @A varchar(8000),
    @B int,
    @C datetime
AS begin
    declare @where varchar(8000)
    declare @sql varchar(8000)
    set @sql='select * from table where 1=1'
    set @where = ''
    set @where = @where + isnull(' and a like '''+@A+'%''','')
    set @where = @where + isnull(' and b = '+cast(@B as varchar),'')
    set @where = @where + isnull(' and c = '''+convert(varchar,@C,120)+'''','')
    set @sql = @sql + @where + ' order by a,b,c'
    exec(@sql) 
end
GO 

CREATE PROCEDURE pro_sample 
    @A varchar(8000),
    @B int,
    @C datetime
AS begin
    declare @where varchar(8000)
    declare @sql varchar(8000)
    set @sql='select * from table where 1=1 '
    set @where = ''
    set @where = @where + isnull(' and a like '''+@A+'%''','')+ isnull(' and b = '+cast(@B as varchar),'')+ isnull(' and c = '''+convert(varchar,@C,120)+'''','')+ ' order by a,b,c'
    set @sql = @sql + @where 
    exec(@sql) 
end