sql数据库自定义函数，比较一行中多个字段的最大值（类似orcal中的greatest）

最大最小都可以中这种方法比较

--drop function  gret
create function dbo.gret (@r0 money,@r1 money,@r2 money,@r3 money,@r4 money,@r5 money,@r6 money,@r7 money)
returns money
as
begin
  declare @tmp money
  set @tmp = @r0
  if(@tmp < @r1)
    set @tmp = @r1
  if(@tmp < @r2)
    set @tmp = @r2
  if(@tmp < @r3)
    set @tmp = @r3
  if(@tmp < @r4)
    set @tmp = @r4
  if(@tmp < @r5)
    set @tmp = @r5
  if(@tmp < @r6)
    set @tmp = @r6
  if(@tmp < @r7)
    set @tmp = @r7
  return @tmp
end