Question

我有一个按位枚举，FlagsAttribute就像这样设置 -

[FlagsAttribute]
public enum MyEnum
{
    None = 0,
    First = 1,
    Second = 2,
    Third = 4,
    Five = 8,
    Six = 16,
    Seven = 32,
    Eight = 64,
    Nine = 128
}

现在，在C＃中，我将此值存储在属性中，例如MyProperty，在保存时，我在整数列的SQL数据库中写入此属性。假设我从代码中选择First,Second,Five，然后在数据库中将其保存为'11'。

我知道我可以从DB获取值，只需要将值转换为MyEnum，它就会给我值。但是，我希望在一些存储过程中对SQL数据进行一些操作，显然我不能将它转换为Enum值。那么，有没有办法可以让我了解个人价值观。

在示例中，如果存储了11，我可以将其作为"1+2+8"

的任何方式

Answer 1

这可能有助于您入门：

Select 11 & 1 As 'First'
  , 11 & 2 As 'Second'
  , 11 & 4 As 'Third'
  , 11 & 8 As 'Five'
  , 11 & 16 As 'Six'
  , 11 & 32 As 'Seven'
  , 11 & 64 As 'Eight'
  , 11 & 128 As 'Nine';

11是您的储值。

这将为设置的每个值返回非零值（即Select 11 & 1 As 'First'返回1，Select 11 & 2 As 'Second'返回2，Select 11 & 4 As 'Third'返回0并且等等。

Answer 2

您可以执行bitwise operations in SQL

Select  *
From    MyTable
Where   MyEnum = (1 | 2 | 8)

返回设置了哪些标志

Select  Case when (MyEnum & 1) = 1 Then 1 else 0 End as First,
        Case when (MyEnum & 2) = 2 Then 1 else 0 End as Second,
        Case when (MyEnum & 4) = 4 Then 1 else 0 End as Third,
        Case when (MyEnum & 8) = 8 Then 1 else 0 End as Fourth,
        Case when (MyEnum & 16) = 16 Then 1 else 0 End as Fifth
From    MyTable

Answer 3

declare @MyEnum as Int
set @MyEnum = 11
select
  case when ( @MyEnum & 1 ) = 1 then '1+' else '' end +
  case when ( @MyEnum & 2 ) = 2 then '2+' else '' end +
  case when ( @MyEnum & 4 ) = 4 then '4+' else '' end +
  case when ( @MyEnum & 8 ) = 8 then '8+' else '' end
  as Bitses

（可能的）尾随加号留给读者练习。

Answer 4

ID  Name
1   Zero
2   One
4   Two
8   Three
16  Four
32  Five

26（或11010）的值对应于One + Three + Four 要获得相关描述，您可以使用下一个请求

DECLARE @Names VARCHAR(8000) 
SELECT @Names = COALESCE(@Names + ' | ', '') + Name 
  FROM [Play].[dbo].[Enums]
  where (26 & ID)=ID
Select @Names;

它会为您提供下一个结果One | Three | Four

如果你想得到ids

DECLARE @Names VARCHAR(8000) 
SELECT @Names = COALESCE(@Names + ', ', '') + STR(ID)
  FROM [Play].[dbo].[Enums]
  where (26 & ID)=ID
Select @Names;

将按位枚举映射到sql列值

4 个答案: