乘车路线查询

-- 模拟数据
SET NOCOUNT ON
IF OBJECT_ID(N'tempdb..#tb') IS NOT NULL
DROP TABLE #tb
CREATE TABLE #tb(
id int IDENTITY
PRIMARY KEY,
lineID int,
state nvarchar(10),
orderid int
)
INSERT #tb(
lineID, state, orderid)
SELECT 1, N'广州东', 1 UNION ALL
SELECT 1, N'体育中心', 2 UNION ALL
SELECT 1, N'体育西', 3 UNION ALL
SELECT 1, N'烈士陵园', 4 UNION ALL
SELECT 1, N'公园前', 5 UNION ALL
SELECT 1, N'西门口', 6 UNION ALL
SELECT 2, N'火车站', 1 UNION ALL
SELECT 2, N'纪念堂', 2 UNION ALL
SELECT 2, N'公园前', 3 UNION ALL
SELECT 2, N'中大', 4 UNION ALL
SELECT 2, N'客村', 5 UNION ALL
SELECT 2, N'琶洲', 6 UNION ALL
SELECT 2, N'万胜围', 7 UNION ALL
SELECT 3, N'广州东', 1 UNION ALL
SELECT 3, N'体育西', 2 UNION ALL
SELECT 3, N'珠江新城', 3 UNION ALL
SELECT 3, N'客村', 4 UNION ALL
SELECT 3, N'市桥', 5 UNION ALL
SELECT 4, N'万胜围', 1 UNION ALL
SELECT 4, N'金洲', 2

CREATE INDEX IX_lineID
ON #tb(
lineID)

CREATE INDEX IX_state
ON #tb(
state)

CREATE INDEX IX_orderid
ON #tb(
orderid)
GO

--处理方法：
--之前也有发表过一些如何处理这个问题的方法，但效率不是太好。下面的这种方法加上了乘车方向的考虑：
--同一条线路上，只有两个乘车方向，而且一旦方向了，就不会再反向乘车（因为是从这个方向来，再坐回去
--是不合理的）；如果某个站点可以换到另一条线路，则换乘后的另一条线路也是两个方向乘车。通过乘车方
--向的控制，减少了算法要搜索的路径。
-- 乘车路线查询
DECLARE
@state_start nvarchar(10),
@state_stop nvarchar(10)
SELECT
@state_start = N'广州东',
@state_stop = N'中大'

-- 查询
IF OBJECT_ID(N'tempdb..#re') IS NOT NULL
DROP TABLE #re
CREATE TABLE #re(
ID int IDENTITY
PRIMARY KEY,
path nvarchar(4000),
state_count int,
line_count int,
start_lineID int,
start_state nvarchar(10),
current_lineID int,
current_state nvarchar(10),
next_orderid int,
flag int,
lineIDs nvarchar(4000),
level int
)

CREATE INDEX IX_current_lineID
ON #re(
current_lineID )

CREATE INDEX IX_current_state
ON #re(
current_state )

CREATE INDEX IX_next_orderid
ON #re(
next_orderid )

CREATE INDEX IX_current_level
ON #re(
level )

DECLARE
@level int,
@rows int
SET
@level = 0

-- 开始
INSERT #re(
path,
state_count, line_count,
start_lineID, start_state,
current_lineID, current_state,
next_orderid, flag, lineIDs, level)
SELECT
path = CONVERT(nvarchar(4000),
RTRIM(A.lineID) + N'{'
+ RTRIM(A.orderid) + N'.' + A.state
),
state_count = 0,
line_count = 0,
start_lineID = A.lineID,
start_state = A.state,
current_lineID = A.lineID,
current_state = A.state,
next_orderid = A.orderid,
flag = CASE
WHEN A.state = @state_stop THEN 0
ELSE NULL END,
lineIDs = ',' + RTRIM(A.lineID) + ',',
level = -(@level + 1)
FROM #tb A
WHERE state = @state_start
SET @rows = @@ROWCOUNT
WHILE @rows > 0
BEGIN
SELECT
@level = @level + 1
INSERT #re(
path,
state_count, line_count,
start_lineID, start_state,
current_lineID, current_state,
next_orderid, flag, lineIDs, level)
-- 同一LineID
SELECT
path = CONVERT(nvarchar(4000),
A.path
+ N'->'
+ RTRIM(B.orderid) + N'.' + B.state
),
state_count = A.state_count + 1,
A.line_count,
A.start_lineID, A.start_state,
current_lineID = B.lineID,
current_state = B.state,
next_orderid = B.orderid + A.flag,
flag = CASE
WHEN B.state = @state_stop THEN 0
ELSE A.flag END,
A.lineIDs,
level = @level
FROM #re A, #tb B
WHERE A.flag <> 0
AND A.level = @level - 1
AND A.current_lineID = B.lineID
AND A.next_orderid = B.orderid

UNION ALL
-- 不同LineID
SELECT
path = CONVERT(nvarchar(4000),
A.path + N'}->'
+ RTRIM(B.lineID) + N'{'
+ RTRIM(B.orderid) + N'.' + B.state
),
state_count = A.state_count + 1,
line_count = A.line_count + 1,
A.start_lineID, A.start_state,
current_lineID = B.lineID,
current_state = B.state,
next_orderid = B.orderid,
flag = CASE
WHEN B.state = @state_stop THEN 0
ELSE NULL END,
A.lineIDs + RTRIM(B.lineID) + ',',
level = - @level
FROM #re A, #tb B
WHERE A.flag <> 0
AND state_count = @level - 1
AND A.current_lineID <> B.lineID
AND A.current_state = B.state
AND NOT EXISTS(
SELECT * FROM #re
WHERE CHARINDEX(',' + RTRIM(B.lineID) + ',', A.lineIDs) > 0)
SET @rows = @@ROWCOUNT

INSERT #re(
path,
state_count, line_count,
start_lineID, start_state,
current_lineID, current_state,
next_orderid, flag, lineIDs, level)
-- 不同LineID 的第站正向
SELECT
path = CONVERT(nvarchar(max),
A.path
+ N'->'
+ RTRIM(B.orderid) + N'.' + B.state
),
state_count = A.state_count + 1,
A.line_count,
A.start_lineID, A.start_state,
current_lineID = B.lineID,
current_state = B.state,
next_orderid = B.orderid + 1,
flag = CASE
WHEN B.state = @state_stop THEN 0
ELSE 1 END,
A.lineIDs,
level = @level
FROM #re A, #tb B
WHERE A.flag IS NULL
AND A.level = - @level
AND A.current_lineID = B.lineID
AND A.next_orderid + 1 = B.orderid
UNION ALL
-- 不同LineID 的第站反向
SELECT
path = CONVERT(nvarchar(max),
A.path
+ N'->'
+ RTRIM(B.orderid) + N'.' + B.state
),
state_count = A.state_count + 1,
A.line_count,
A.start_lineID, A.start_state,
current_lineID = B.lineID,
current_state = B.state,
next_orderid = B.orderid - 1,
flag = CASE
WHEN B.state = @state_stop THEN 0
ELSE - 1 END,
A.lineIDs,
level = @level
FROM #re A, #tb B
WHERE A.flag IS NULL
AND A.level = - @level
AND A.current_lineID = B.lineID
AND A.next_orderid - 1 = B.orderid

SET @rows = @rows + @@ROWCOUNT
END

SELECT
-- *,
path = path + N'}',
line_count,
state_count
FROM #re
WHERE flag = 0

/*

pathline_countstate_count
3{1.广州东->2.体育西->3.珠江新城->4.客村}->2{5.客村->4.中大}15
3{1.广州东->2.体育西}->1{3.体育西->4.烈士陵园->5.公园前}->2{3.公园前->4.中大}26
1{1.广州东->2.体育中心->3.体育西->4.烈士陵园->5.公园前}->2{3.公园前->4.中大}16
1{1.广州东->2.体育中心->3.体育西}->3{2.体育西->3.珠江新城->4.客村}->2{5.客村->4.中大}27

*/