Question

我有这个存储过程：

ALTER PROCEDURE [dbo].[GetCalendarEvents]
    (@StartDate datetime, 
     @EndDate datetime, 
     @Location varchar(250) = null)
AS
BEGIN
    SELECT * 
    FROM Events 
    WHERE EventDate >= @StartDate 
      AND EventDate <= @EndDate 
      AND (Location IS NULL OR Location = @Location)
END

现在，我有location参数，我想要做的是如果参数不为null，那么在where子句中包含参数。如果参数为null，我想完全忽略where参数，只能通过开始和结束日期获得结果。

因为当我这样做时：

EXEC GetCalendarEvents '02/02/2014', '10/10/2015', null

我没有得到任何结果，因为有其他位置不为null，并且由于location参数为null，我想从所有位置获取结果。

我知道如何解决这个问题？

谢谢，Laziale

Answer 1

ALTER PROCEDURE [dbo].[GetCalendarEvents]
( @StartDate DATETIME,
  @EndDate DATETIME,
  @Location VARCHAR(250) = NULL
)
AS
BEGIN
    SELECT  *
    FROM    events
    WHERE   EventDate >= @StartDate
            AND EventDate <= @EndDate
            AND Location = ISNULL(@Location, Location )
END

如果有可能是NULL列，那么这将有效。

ALTER PROCEDURE [dbo].[GetCalendarEvents]
( @StartDate DATETIME,
  @EndDate DATETIME,
  @Location VARCHAR(250) = NULL
)
AS
BEGIN
    IF ( @loc IS NULL )
        BEGIN
            SELECT  *
            FROM    events
            WHERE   EventDate >= @StartDate
                    AND EventDate <= @EndDate
        END
    ELSE
        BEGIN
            SELECT  *
            FROM    events
            WHERE   EventDate >= @StartDate
                    AND EventDate <= @EndDate
                    AND Location = @Location
        END
END

有一个＆＃39; OR＆＃39;由于可能存在性能问题，应合理避免使用该条款。

Answer 2

然后应该阅读WHERE子句中的部分

AND (@Location IS NULL OR Location=@Location)

Answer 3

试试这个

 SELECT * 
    FROM Events 
    WHERE EventDate >= @StartDate 
      AND EventDate <= @EndDate 
      AND Location = Case When LEN(@Location) > 0 Then  @Location Else Location End

Answer 4

可以使用动态SQL查询轻松完成。

ALTER PROCEDURE [dbo].[GetCalendarEvents]
(@StartDate datetime, 
 @EndDate datetime, 
 @Location varchar(250) = null)
AS
BEGIN
   DECLARE @SQL NVARCHAR(MAX);
   DECLARE @PARAMETER_DEFIINITION NVARCHAR(MAX);
   DECLARE @WHERE_PART NVARCHAR(MAX);

   SET @PARAMETER_DEFIINITION =' @StartDate DATETIME, @EndDate DATETIME, @Location VARCHAR(250) '

   SET @SQL ='SELECT * 
              FROM Events 
              WHERE EventDate >= @StartDate 
              AND EventDate <= @EndDate '

   IF @Location IS NOT NULL
   BEGIN
       SET @WHERE_PART = ' AND Location  = @Location '
   END    

   SET @SQL = @SQL + @WHERE_PART
   EXEC SP_EXECUTESQL @SQL, @PARAMETER_DEFIINITION, @StartDate, @EndDate, @Location
END

将根据参数动态创建查询。在这里，如果@location为null，那么它将不会添加到where部分。

如果您想要更多编写动态查询，请参阅此文章。 http://codingpulse.blogspot.com/2015/02/dynamic-sql-in-stored-procedure-part-1.html

SQL Server存储过程可选参数，包括所有if null

4 个答案: