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T-SQL:如何从存储过程中返回0行,以及如何使用XACT\u ABORT和TRY/CATCH

stored-procedures tsql sql-server-2005 sql-server sql

Michael Waterfall · 技术社区 · 16 年前

我正在编写一个存储过程,当某些操作失败时,我希望返回0条记录。我似乎不知道如何只返回0行?我用过 SELECT NULL NULL 在第1行第1列。我也尝试过不指定任何 SELECT 语句,但在测试 @@ROWCOUNT 从未从 SP中前面的语句(在 EXISTS() ). 如有任何建议,将不胜感激。

另外,我还有 XACT_ABORT 设置为ON,但我也使用了 TRY/CATCH 块以确保从存储过程返回正确的错误“return value”。这样行吗?如果出现错误 XACT\u中止 覆盖 尝试/抓住 或者我的错误代码路径仍然会导致返回正确的返回值吗?

-- Setup
SET NOCOUNT ON; -- SET NOCOUNT ON added to prevent extra result sets from interfering with SELECT statements.
SET XACT_ABORT ON; -- SET XACT_ABORT ON rollback transactions on errors
DECLARE @return int; SET @return = 1; -- Default to general error

-- Start transaction
BEGIN TRANSACTION
    BEGIN TRY

        IF NOT EXISTS(SELECT NULL FROM [MyTable] WHERE [Check] = 1) 
        BEGIN

            -- Insert new record    
            INSERT INTO [MyTable] (Check, Date) VALUES (1, GETDATE());
            SELECT SCOPE_IDENTITY() AS [MyValue]; -- Return 1 row
            SET @return = 0; -- Success

        END
        ELSE
        BEGIN

            -- Fail
            SELECT NULL AS [MyValue]; -- Want to return 0 rows not 1 row with NULL
            SET @return = 2; -- Fail error

        END

    END TRY
    BEGIN CATCH

        -- Error
        ROLLBACK TRANSACTION;
        SELECT NULL AS [MyValue]; -- Want to return 0 rows not 1 row with NULL
        SET @return = 1; -- General error

    END CATCH

-- End transaction and return
COMMIT TRANSACTION
RETURN @return;

2 回复 | 直到 16 年前

AdaTheDev 16 年前

SELECT TOP 0 NULL AS MyValue

就我个人而言,我会为这个存储过程使用一个输出参数来返回ID,而不是返回一个resultset——这只是我的首选。然后只需将输出参数设置为默认值,例如-1,以指示未执行任何操作。

KM. 16 年前

我会这样做:

CREATE PROCEDURE YourProcedure
AS
(   @NewMyValue  int OUTPUT   --<<<<<use output parameter and not a result set
)
BEGIN TRY

    --<<<<put everything in the BEGIN TRY!!!

    -- Setup
    SET NOCOUNT ON; -- SET NOCOUNT ON added to prevent extra result sets from interfering with SELECT statements.
    SET XACT_ABORT ON; -- SET XACT_ABORT ON rollback transactions on errors
    DECLARE @return int

    --<<init multiple variables in a select, it is faster than multiple SETs
    --set defaults
    SELECT @return = 1       -- Default to general error
          ,@NewMyValue=NULL

    -- Start transaction
    BEGIN TRANSACTION  --<<<put the transaction in the BEGIN TRY

    --<<<lock rows for this transaction using UPDLOCK & HOLDLOCK hints
    IF NOT EXISTS(SELECT NULL FROM [MyTable] WITH (UPDLOCK, HOLDLOCK) WHERE [Check] = 1)
    BEGIN
            -- Insert new record    
        INSERT INTO [MyTable] (Check, Date) VALUES (1, GETDATE());
        SELECT @NewMyValue=SCOPE_IDENTITY()  --<<<set output parameter, no result set
              ,@return = 0; -- Success
    END
    ELSE
    BEGIN
        -- Fail
        --<<no need for a result set!!! output parameter was set to a default of NULL
        SET @return = 2; -- Fail error
    END

    COMMIT TRANSACTION  --<<<commit in the BEGIN TRY!!!
END TRY
BEGIN CATCH
    -- Error
    IF XACT_STATE()!=0  --<<<only rollback if there is a bad transaction
    BEGIN
        ROLLBACK TRANSACTION
    END
    --<<any insert(s) into log tables, etc
    --<<no need for a result set!!! output parameter was set to a default of NULL
    SET @return = 1; -- General error
END CATCH

-- End transaction and return
RETURN @return;
GO