SQL Server 2008 存储过程优化

Question

我有一个存储过程，它非常简单，只有一个选择语句，但是 where 子句会根据参数而变化。

我正在使用 if else 语句并写出选择 4 次，有没有更好的方法来简化这个存储过程？

    IF @Status > 0 
        BEGIN
            IF @Group = ''
                BEGIN
                    SELECT  *
                    FROM    ( SELECT    tbl.* ,
                                        ROW_NUMBER() OVER ( ORDER BY tbl.NDB_No ) rownum
                              FROM      dbo.FoodAbbrev AS tbl
                              WHERE     Status = @Status
                            ) seq
                    WHERE   seq.rownum BETWEEN @X AND @Y
                    ORDER BY seq.rownum
                END
            ELSE 
                BEGIN
                    SELECT  *
                    FROM    ( SELECT    tbl.* ,
                                        ROW_NUMBER() OVER ( ORDER BY tbl.NDB_No ) rownum
                              FROM      dbo.FoodAbbrev AS tbl
                              WHERE     Status = @Status
                                        AND GroupCd = @Group
                            ) seq
                    WHERE   seq.rownum BETWEEN @X AND @Y
                    ORDER BY seq.rownum
                END
        END
    ELSE 
        BEGIN
            IF @Group = ''
                BEGIN
                    SELECT  *
                    FROM    ( SELECT    tbl.* ,
                                        ROW_NUMBER() OVER ( ORDER BY tbl.NDB_No ) rownum
                              FROM      dbo.FoodAbbrev AS tbl
                            ) seq
                    WHERE   seq.rownum BETWEEN @X AND @Y
                    ORDER BY seq.rownum
                END
            ELSE 
                BEGIN
                    SELECT  *
                    FROM    ( SELECT    tbl.* ,
                                        ROW_NUMBER() OVER ( ORDER BY tbl.NDB_No ) rownum
                              FROM      dbo.FoodAbbrev AS tbl
                              WHERE     GroupCd = @Group
                            ) seq
                    WHERE   seq.rownum BETWEEN @X AND @Y
                    ORDER BY seq.rownum
                END
        END
END

Answer 1

将所有这些IF语句替换为以下带有可选参数SELECT语句：

   SELECT  *
   FROM    ( SELECT    tbl.* ,
             ROW_NUMBER() OVER ( ORDER BY tbl.NDB_No ) rownum
             FROM      dbo.FoodAbbrev AS tbl
             WHERE     1 = 1
             AND (@Group IS NULL OR GroupCd = @Group)
             AND (@Status IS NULL OR Status = @Status)
   ) seq
   WHERE   seq.rownum BETWEEN @X AND @Y
   ORDER BY seq.rownum

Answer 2

                SELECT  *
                FROM    ( SELECT    tbl.* ,
                                    ROW_NUMBER() OVER ( ORDER BY tbl.NDB_No ) rownum
                          FROM      dbo.FoodAbbrev AS tbl
                          WHERE     ISNULL(Status,0) = CASE WHEN @Status > 0 THEN @Status ELSE ISNULL(Status,0) END
                          AND       ISNULL(GroupCd, '') = CASE WHEN @Group = '' THEN ISNULL(GroupCd, '') ELSE @Group END
                        ) seq
                WHERE   seq.rownum BETWEEN @X AND @Y
                ORDER BY seq.rownum