@@OPTIONS (Transact-SQL)

项目
10/16/2024

适用于： SQL Server Azure SQL 数据库 Azure SQL 托管实例

返回有关当前 SET 选项的信息。

语法

@@OPTIONS

返回类型

integer

注解

选项可能来自 SET 命令的使用或来自 sp_configure user options 值。使用 SET 命令配置的会话值会替代 sp_configure 选项。许多工具（例如 Management Studio）会自动配置设置选项。每个用户都有一个表示配置的 @@OPTIONS 函数。

可以使用 SET 语句更改特定用户会话的语言和查询处理选项。 @@OPTIONS 只能检测到设置为 ON 或 OFF 的选项。

@@OPTIONS 函数返回选项的位图，转换为基数为 10 的（十进制）整数。配置 user options 服务器配置选项一文提供的表中介绍了位设置的存放位置。

要解码 @@OPTIONS 值，将 @@OPTIONS 返回的整数转换为二进制，然后查找配置 user options 服务器配置选项中的表中的值。例如，如果 SELECT @@OPTIONS; 返回值 5496，使用 Windows 编程人员计算器 (calc.exe) 将十进制 5496 转换为二进制。结果为 1010101111000。最右边的字符（二进制 1、2 和 4）为 0，指示表中的前三项为关闭状态。查询该表，可以看到这三项是 DISABLE_DEF_CNST_CHK、IMPLICIT_TRANSACTIONS 和 CURSOR_CLOSE_ON_COMMIT。下一项（1000 位置中的 ANSI_WARNINGS）处于启用状态。继续向左处理位图并向下处理选项列表。如果最左边的选项是 0，则它们被类型转换截断。位图 1010101111000 实际上是 001010101111000，代表全部 15 个选项。

示例 C 提供自动将 @@OPTIONS 位掩码映射到用户选项的查询。

示例

A. 更改如何影响行为的演示

下面的示例演示采用 CONCAT_NULL_YIELDS_NULL 选项的两个不同设置的连结行为的区别。

SELECT @@OPTIONS AS OriginalOptionsValue;
SET CONCAT_NULL_YIELDS_NULL OFF;
SELECT 'abc' + NULL AS ResultWhen_OFF, @@OPTIONS AS OptionsValueWhen_OFF;
  
SET CONCAT_NULL_YIELDS_NULL ON;
SELECT 'abc' + NULL AS ResultWhen_ON, @@OPTIONS AS OptionsValueWhen_ON;

B. 测试客户端 NOCOUNT 设置

以下示例设置 NOCOUNT``ON 并测试 @@OPTIONS 的值。 NOCOUNT``ON 选项可防止将会话中每一个语句的有关受影响行数的消息发送回请求的客户端。 @@OPTIONS 的值设置为 512 (0x0200)。这表示 NOCOUNT 选项。下面的示例测试客户端是否启用了 NOCOUNT 选项。例如，它可以帮助跟踪客户端的性能差异。

SET NOCOUNT ON
IF @@OPTIONS & 512 > 0
RAISERROR ('Current user has SET NOCOUNT turned on.', 1, 1)

C. 使用 PIVOT 查询查看 @@OPTIONS 位掩码

以下示例使用表值构造函数生成数字列表引用，然后通过位掩码运算符比较 @@OPTIONS 的值。 APPLY 子句执行字符串串联以生成字符位掩码，另一个子句生成别名，以便根据配置 user options 项服务器配置选项中的记录值进行查看。

SELECT S.Bits,
    Flags.*
FROM (
    SELECT optRef,
        posRef,
        flagCheck
    FROM (
        SELECT ones.n + tens.n * 10
        FROM ( VALUES (0), (1), (2), (3), (4), (5), (6), (7), (8), (9) ) ones(n),
            ( VALUES (0), (1), (2), (3), (4), (5), (6), (7), (8), (9) ) tens(n)
        ) f1(powRef)
    CROSS APPLY (
        SELECT POWER(2, powRef)
        WHERE powRef <= 16
        ) f2(binRef)
    CROSS JOIN (
        VALUES (@@OPTIONS)
        ) f3(optRef)
    CROSS APPLY (
        SELECT (optRef & binRef) / binRef
        ) f4(flagRef)
    CROSS APPLY (
        SELECT RIGHT(CONVERT(VARCHAR(2), CAST(powRef AS VARBINARY(1)), 2), 1) [posRef],
            CAST(flagRef AS INT) [flagCheck]
        ) pref
    ) TP
PIVOT( MAX( flagCheck ) FOR posRef IN ( [0], [1], [2], [3], [4], [5], [6], [7], [8], [9], [A], [B], [C], [D], [E], [F] )) P
CROSS APPLY (
    SELECT CONCAT ( '', [0], [1], [2], [3], [4], [5], [6], [7], [8], [9], [A], [B], [C], [D], [E], [F] ),
        CONCAT ( '', [F], [E], [D], [C], [B], [A], [9], [8], [7], [6], [5], [4], [3], [2], [1], [0] )
    ) S (stib, Bits)
CROSS APPLY (
    SELECT
          CAST(P.[0] AS BIT) /* 1     */ [DISABLE_DEF_CNST_CHK] -- Controls interim or deferred constraint checking.
        , CAST(P.[1] AS BIT) /* 2     */ [IMPLICIT_TRANSACTIONS] -- For dblib network library connections, controls whether a transaction is started implicitly when a statement is executed. The IMPLICIT_TRANSACTIONS setting has no effect on ODBC or OLEDB connections.
        , CAST(P.[2] AS BIT) /* 4     */ [CURSOR_CLOSE_ON_COMMIT] -- Controls behavior of cursors after a commit operation has been performed.
        , CAST(P.[3] AS BIT) /* 8     */ [ANSI_WARNINGS] -- Controls truncation and NULL in aggregate warnings.
        , CAST(P.[4] AS BIT) /* 16    */ [ANSI_PADDING] -- Controls padding of fixed-length variables.
        , CAST(P.[5] AS BIT) /* 32    */ [ANSI_NULLS] -- Controls NULL handling when using equality operators.
        , CAST(P.[6] AS BIT) /* 64    */ [ARITHABORT] -- Terminates a query when an overflow or divide-by-zero error occurs during query execution.
        , CAST(P.[7] AS BIT) /* 128   */ [ARITHIGNORE] -- Returns NULL when an overflow or divide-by-zero error occurs during a query.
        , CAST(P.[8] AS BIT) /* 256   */ [QUOTED_IDENTIFIER] -- Differentiates between single and double quotation marks when evaluating an expression.
        , CAST(P.[9] AS BIT) /* 512   */ [NOCOUNT] -- Turns off the message returned at the end of each statement that states how many rows were affected.
        , CAST(P.[A] AS BIT) /* 1024  */ [ANSI_NULL_DFLT_ON] -- Alters the session's behavior to use ANSI compatibility for nullability. New columns defined without explicit nullability are defined to allow nulls.
        , CAST(P.[B] AS BIT) /* 2048  */ [ANSI_NULL_DFLT_OFF] -- Alters the session's behavior not to use ANSI compatibility for nullability. New columns defined without explicit nullability do not allow nulls.
        , CAST(P.[C] AS BIT) /* 4096  */ [CONCAT_NULL_YIELDS_NULL] -- Returns NULL when concatenating a NULL value with a string.
        , CAST(P.[D] AS BIT) /* 8192  */ [NUMERIC_ROUNDABORT] -- Generates an error when a loss of precision occurs in an expression.
        , CAST(P.[E] AS BIT) /* 16384 */ [XACT_ABORT] -- Rolls back a transaction if a Transact-SQL statement raises a run-time error.*/
    ) AS Flags;

D. 使用 GET_BIT 查看 @@OPTIONS 位掩码

适用于：SQL Server 2022 (16.x) 及更高版本。

以下示例使用 GET_BIT 函数从 @@OPTIONS 中的每个特定位获取值。

SELECT
      GET_BIT(@@OPTIONS, 0)  /* 1     */ AS [DISABLE_DEF_CNST_CHK] -- Controls interim or deferred constraint checking.
    , GET_BIT(@@OPTIONS, 1)  /* 2     */ AS [IMPLICIT_TRANSACTIONS] -- For dblib network library connections, controls whether a transaction is started implicitly when a statement is executed. The IMPLICIT_TRANSACTIONS setting has no effect on ODBC or OLEDB connections.
    , GET_BIT(@@OPTIONS, 2)  /* 4     */ AS [CURSOR_CLOSE_ON_COMMIT] -- Controls behavior of cursors after a commit operation has been performed.
    , GET_BIT(@@OPTIONS, 3)  /* 8     */ AS [ANSI_WARNINGS] -- Controls truncation and NULL in aggregate warnings.
    , GET_BIT(@@OPTIONS, 4)  /* 16    */ AS [ANSI_PADDING] -- Controls padding of fixed-length variables.
    , GET_BIT(@@OPTIONS, 5)  /* 32    */ AS [ANSI_NULLS] -- Controls NULL handling when using equality operators.
    , GET_BIT(@@OPTIONS, 6)  /* 64    */ AS [ARITHABORT] -- Terminates a query when an overflow or divide-by-zero error occurs during query execution.
    , GET_BIT(@@OPTIONS, 7)  /* 128   */ AS [ARITHIGNORE] -- Returns NULL when an overflow or divide-by-zero error occurs during a query.
    , GET_BIT(@@OPTIONS, 8)  /* 256   */ AS [QUOTED_IDENTIFIER] -- Differentiates between single and double quotation marks when evaluating an expression.
    , GET_BIT(@@OPTIONS, 9)  /* 512   */ AS [NOCOUNT] -- Turns off the message returned at the end of each statement that states how many rows were affected.
    , GET_BIT(@@OPTIONS, 10) /* 1024  */ AS [ANSI_NULL_DFLT_ON] -- Alters the session's behavior to use ANSI compatibility for nullability. New columns defined without explicit nullability are defined to allow nulls.
    , GET_BIT(@@OPTIONS, 11) /* 2048  */ AS [ANSI_NULL_DFLT_OFF] -- Alters the session's behavior not to use ANSI compatibility for nullability. New columns defined without explicit nullability do not allow nulls.
    , GET_BIT(@@OPTIONS, 12) /* 4096  */ AS [CONCAT_NULL_YIELDS_NULL] -- Returns NULL when concatenating a NULL value with a string.
    , GET_BIT(@@OPTIONS, 13) /* 8192  */ AS [NUMERIC_ROUNDABORT] -- Generates an error when a loss of precision occurs in an expression.
    , GET_BIT(@@OPTIONS, 14) /* 16384 */ AS [XACT_ABORT] -- Rolls back a transaction if a Transact-SQL statement raises a run-time error.*/
GO

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