130.最短乘车路线查询-案例

Bertha 。 2024-02-19 19:08 32阅读 0赞

CREATE TABLE T_Line(
    ID      nvarchar(10),  --公交线路号
    Station nvarchar(10),  --站点名称
    Orders  int)           --行车方向(通过它反应每个站的上一个、下一个站)
    INSERT T_Line 
    SELECT N'8路'  ,N'站A',1 UNION ALL
    SELECT N'8路'  ,N'站B',2 UNION ALL
    SELECT N'8路'  ,N'站C',3 UNION ALL
    SELECT N'8路'  ,N'站D',4 UNION ALL
    SELECT N'8路'  ,N'站J',5 UNION ALL
    SELECT N'8路'  ,N'站L',6 UNION ALL
    SELECT N'8路'  ,N'站M',7 UNION ALL
    SELECT N'20路' ,N'站G',1 UNION ALL
    SELECT N'20路' ,N'站H',2 UNION ALL
    SELECT N'20路' ,N'站I',3 UNION ALL
    SELECT N'20路' ,N'站J',4 UNION ALL
    SELECT N'20路' ,N'站L',5 UNION ALL
    SELECT N'20路' ,N'站M',6 UNION ALL
    SELECT N'255路',N'站N',1 UNION ALL
    SELECT N'255路',N'站O',2 UNION ALL
    SELECT N'255路',N'站P',3 UNION ALL
    SELECT N'255路',N'站Q',4 UNION ALL
    SELECT N'255路',N'站J',5 UNION ALL
    SELECT N'255路',N'站D',6 UNION ALL
    SELECT N'255路',N'站E',7 UNION ALL
    SELECT N'255路',N'站F',8
    GO
    
    --乘车线路查询存储过程
    CREATE PROC p_qry
    @Station_Start nvarchar(10),
    @Station_Stop  nvarchar(10)
    AS
    SET NOCOUNT ON
    DECLARE @l int
    SET @l=0
    SELECT ID,Station,
    	Line=CAST('('+RTRIM(ID)+': '+RTRIM(Station) as nvarchar(4000)),
    	Orders=Orders,
    	[Level]=@l
    INTO # FROM T_Line
    WHERE Station=@Station_Start
    WHILE @@ROWCOUNT>0 
    	AND NOT EXISTS(SELECT * FROM # WHERE Station=@Station_Stop)
    BEGIN
    	SET @l=@l+1
    	INSERT #(Line,ID,Station,Orders,[Level])
    	SELECT 
    		Line=a.Line+CASE
    			WHEN a.ID=b.ID THEN N'->'+RTRIM(b.Station)
    			ELSE N') ∝ ('+RTRIM(b.ID)
    				+N': '+RTRIM(b.Station) END,
    		b.ID,b.Station,b.Orders,@l
    	FROM # a,T_Line b
    	WHERE a.[Level]=@l-1
    		AND(a.Station=b.Station AND a.ID<>b.ID
    			OR a.ID=b.ID AND(
    				a.Orders=b.Orders+1
    				OR
    				a.Orders=b.Orders-1))
    		AND LEN(a.Line)<4000
    		AND PATINDEX('%[ >]'+b.Station+'[-)]%',a.Line)=0
    END
    SELECT N'起点站'=@Station_Start
    	,N'终点站'=@Station_Stop
    	,N'乘车线路'=Line+N')' 
    FROM # 
    WHERE [Level]=@l 
    	AND Station=@Station_Stop
    IF @@ROWCOUNT =0 --如果未有可以到达的线路,则显示处理结果表备查
    	SELECT * FROM #
    GO
    
    --调用
    EXEC p_qry N'站A',N'站L'
    /*--结果
    起点站  终点站  乘车线路
    ---------- ------------ -----------------------------------------------------------
    站A    站L    (8路: 站A->站B->站C->站D->站J->站L)
    --*/