T-SQL：如何禁用整数运算的溢出检查？

Posted 2021-04-15

在C＃中，我们使用unchecked来禁用整数运算的溢出检查

int int1;
unchecked
{
    int1 = 2147483647 + 10;
}

整数运算结果将换行到-2,147,483,639

但是在T-SQL中我找不到禁用边界检查的方法

DECLARE @INT1 INT
SET @INT1 = 2147483647 + 10

结果有误：

Msg 8115，Level 16，State 2，Line 2 将表达式转换为数据类型int的算术溢出错误。

答案

不是我认为这一定是一个好主意，但你可以把它包装在try / catch中。

declare @int int;

begin try
  set @int = 2147483647 + 10
end try
begin catch
  if ERROR_NUMBER() = 8115 
    set @int = 2147483647
  else 
    select
        ERROR_NUMBER() AS ErrorNumber  
       ,ERROR_MESSAGE() AS ErrorMessage;  
end catch 

select @int

结果：

2147483647

另一答案

根据Microsoft specification，由于INT数据类型的范围从-2,147,483,648到2,147,483,647，因此无法执行该操作（2147483647 + 10）。

相反，您可以使用BIGINT数据类型，如下所示：

DECLARE @number BIGINT;
SET @number = CAST(2147483647 AS BIGINT) + 10;
SELECT @number;
-- Output: 2147483657, as expected

另一答案

您可以将int值转换为bigint，执行添加然后处理溢出，同时使用int表达式转换回case：

declare @MaxInt as BigInt = Power( Cast( 2 as BigInt ), 31 ) - 1;
declare @Foo as Int = 2147483647;
declare @Bar as Int = 10;
declare @BigSum as BigInt;
set @BigSum = @Foo + Cast( 10 as BigInt );
select @MaxInt as MaxInt, @Foo as Foo, @Bar as Bar, @BigSum as BigSum,
  case when @BigSum <= @MaxInt then Cast( @BigSum as Int ) else
    Cast( @BigSum - Power( Cast( 2 as BigInt ), 32 ) as Int ) end as Unsigned;

更新：一个更整洁的例子，显示如何获取BigInt结果（来自先前的计算）并将其转换为Int而不会溢出：

declare @Samples as Table ( Value BigInt );
insert into @Samples ( Value ) values
  -- NB: At least one literal value needs to be cast as a BigInt to get BigInt values.  No, really.
  ( Cast( 0x0 as BigInt ) ), ( 0x1 ), ( 0x7FFFFFFF ), ( 0x80000000 ), ( 0x80000001 ), ( 0xFFFFFFFF ),
  ( -1 ), ( 0x4200000001 ), ( 0x7080000000 ); -- Some BigInt values beyond 32 bits.

select Value, Cast( Value as Binary(8) ) as ValueHex,
  Value & 0xFFFFFFFF as LSB32, Cast( Value & 0xFFFFFFFF as Binary(8) ) as LSB32Hex,
  Cast( case when Value & 0x80000000 = 0 then Value & 0xFFFFFFFF else
    ( Value & 0x7FFFFFFF ) - Cast( 0x80000000 as BigInt ) end as Int ) as IntResult
  from @Samples;

转换可以捆绑到UDF中，但性能可能会受到影响。