存储过程偶尔意外返回 2 个结果

Question

我有以下存储过程来基于 2 个参数从表中获取数据：

SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
-- =============================================
-- Author:      Dmitry Kreslavskiy
-- Create date: 2015-01-12
-- Description: spGetCreditBenchmarkCurves
-- =============================================
/* spGetCreditBenchmarkCurves
 * Get the list of credit benchmark spread records, if necessary fixing
 * currency and latest ValueDate <= RunDate.
 *     param[in]  RunDate    Run date of the search (uses the last date up to
 *                            this time), NULL = all
 *     param[in]  Ccy        Use only this currency
 *     return     Table (Ccy, ValueDate, TenorSize, TenorUnit, Value)
 */
ALTER PROCEDURE [dbo].[spGetCreditBenchmarkCurves]
(
    @RunDate date       = NULL,
    @Ccy     varchar(3) = NULL
)
AS
BEGIN
    -- SET NOCOUNT ON added to prevent extra result sets from
    -- interfering with SELECT statements.
    SET NOCOUNT ON;
    IF @RunDate IS NULL
       IF @Ccy IS NULL
           SELECT *
             FROM [dbo].CreditBenchmarkCurves
       ELSE -- @Ccy is supplied
             SELECT *
               FROM [dbo].CreditBenchmarkCurves
              WHERE Ccy = @Ccy
    ELSE -- @RunDate is supplied
       /* It could be that the table does not have any valid data on @RunDate,
        * so find the latest date before @RunDate with valid data, and store
        * this in @ExactDate, to use it in a query directly.
        *
        * (Same thing could be done using an INNER JOIN instead of 2 selects,
        *  but it is much clearer code to do it step by step. Also, I have a
        *  feeling this implementation is faster as well.)
        */
       DECLARE @ExactDate date
       SET @ExactDate = (SELECT MAX(ValueDate)
                           FROM [dbo].CreditBenchmarkCurves
                          WHERE ValueDate <= @RunDate)
       IF @Ccy IS NULL
           SELECT *
             FROM [dbo].CreditBenchmarkCurves
            WHERE ValueDate = @ExactDate
       ELSE -- @Ccy is supplied
           SELECT *
             FROM [dbo].CreditBenchmarkCurves
            WHERE ValueDate = @ExactDate AND
                  Ccy       = @Ccy
END
GO

此代码偶尔会返回一个值表，如预期的那样：

EXEC dbo.spGetCreditBenchmarkCurves @RunDate = '2015-02-27', @Ccy = 'AUD'

但是传递默认运行日期会得到一个完整表和一个空表：

EXEC dbo.spGetCreditBenchmarkCurves @RunDate = NULL, @Ccy = 'AUD'
EXEC dbo.spGetCreditBenchmarkCurves

错误是什么，如何使用这样的代码执行 2 个SELECT语句？谢谢

Answer 1

此代码

ALTER PROCEDURE [dbo].[spGetCreditBenchmarkCurves]
(
    @RunDate date       = NULL,
    @Ccy     varchar(3) = NULL
)
AS
BEGIN
    IF @RunDate IS NULL
       IF @Ccy IS NULL
           SELECT *
             FROM [dbo].CreditBenchmarkCurves
       ELSE -- @Ccy is supplied
             SELECT *
               FROM [dbo].CreditBenchmarkCurves
              WHERE Ccy = @Ccy
    ELSE 
       DECLARE @ExactDate date
       SET @ExactDate = (SELECT MAX(ValueDate)
                           FROM [dbo].CreditBenchmarkCurves
                          WHERE ValueDate <= @RunDate)
       IF @Ccy IS NULL
           SELECT *
             FROM [dbo].CreditBenchmarkCurves
            WHERE ValueDate = @ExactDate
       ELSE -- @Ccy is supplied
           SELECT *
             FROM [dbo].CreditBenchmarkCurves
            WHERE ValueDate = @ExactDate AND
                  Ccy       = @Ccy
END

等于：

ALTER PROCEDURE [dbo].[spGetCreditBenchmarkCurves]
(
    @RunDate date       = NULL,
    @Ccy     varchar(3) = NULL
)
AS
BEGIN
    IF @RunDate IS NULL
    BEGIN
       IF @Ccy IS NULL
       BEGIN
           SELECT * FROM [dbo].CreditBenchmarkCurves
       END
       ELSE BEGIN
           SELECT * FROM [dbo].CreditBenchmarkCurves WHERE Ccy = @Ccy
       END
    END
    ELSE BEGIN
       DECLARE @ExactDate date
    END
   SET @ExactDate = (SELECT MAX(ValueDate)
                       FROM [dbo].CreditBenchmarkCurves
                      WHERE ValueDate <= @RunDate)
   IF @Ccy IS NULL
       SELECT *
         FROM [dbo].CreditBenchmarkCurves
        WHERE ValueDate = @ExactDate
   ELSE -- @Ccy is supplied
       SELECT *
         FROM [dbo].CreditBenchmarkCurves
        WHERE ValueDate = @ExactDate AND
              Ccy       = @Ccy
END

如果没有BEGIN END只有DECLARE @ExactDate date被视为 ELSE 块。所以实际上如果@RunDate IS NULL选择将发生 2 次。

Answer 2

用开始/结束包装你的 if else 条件

IF @RunDate IS NULL
BEGIN 
 /* your code for if */
END
ELSE
BEGIN
/* your code for else */
END

注意：

1. BEGIN 和 END 定义了一系列 Transact-SQL 语句，这些语句一起执行。
2. 如果。。。ELSE 构造可以批量使用，在存储过程中，和即席查询

参考 1：MSDN（如果不是）

参考 2：MSDN（如果其他）具有开始结束