坐地鐵有時候不一定要坐最少站的，有時是希望能坐換乘次數最少的，應該怎麼改造才能把所有的方案都取出來，然後按換乘次數、經過站點數依次排序?
lineID state orderid
1 廣州東 1
1 體育中心2
1 體育西 3
1 烈士陵園4
1 公園前 6
1 西門口 7
2 火車站 1
2 紀念堂 2
2 公園前 3
2 中大 4
2 客村 5
2 琶洲 6
2 萬勝圍 7
3 廣州東 1
3 體育西 2
3 珠江新城3
3 客村 4
3 市橋 5
4 萬勝圍 1
4 金洲 2
如上面數據，想查詢“廣州東”至“中大”，大家通過程序計算列出全部的方案。
Peak Wong：
SQL code
DECLARE @tb TABLE(
lineID int, state nvarchar(10), orderid int)
INSERT @tb
SELECT 1, N'廣州東', 1 UNION ALL
SELECT 1, N'體育中心', 2 UNION ALL
SELECT 1, N'體育西', 3 UNION ALL
SELECT 1, N'烈士陵園', 4 UNION ALL
SELECT 1, N'公園前', 6 UNION ALL
SELECT 1, N'西門口', 7 UNION ALL
SELECT 2, N'火車站', 1 UNION ALL
SELECT 2, N'紀念堂', 2 UNION ALL
SELECT 2, N'公園前', 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'萬勝圍', 7 UNION ALL
SELECT 3, N'廣州東', 1 UNION ALL
SELECT 3, N'體育西', 2 UNION ALL
SELECT 3, N'珠江新城', 3 UNION ALL
SELECT 3, N'客村', 4 UNION ALL
SELECT 3, N'市橋', 5 UNION ALL
SELECT 4, N'萬勝圍', 1 UNION ALL
SELECT 4, N'金洲', 2
DECLARE
@state_start nvarchar(10),
@state_stop nvarchar(10)
SELECT
@state_start = N'廣州東',
@state_stop = N'中大'
-- 查詢
DECLARE @re TABLE(
path nvarchar(max),
state_count int,
start_lineID int,
start_state nvarchar(10),
current_lineID int,
current_state nvarchar(10),
current_orderid int,
flag int,
lineIDs nvarchar(max),
level int
)
DECLARE
@level int,
@rows int
SET
@level = 0
-- 開始
INSERT @re
SELECT
path = CONVERT(nvarchar(max),
RTRIM(A.lineID) + N'{'
+ RTRIM(A.orderid) + N'.' + A.state
),
state_count = 0,
start_lineID = A.lineID,
start_state = A.state,
current_lineID = A.lineID,
current_state = A.state,
current_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
-- 同一 LineID
SELECT
path = CONVERT(nvarchar(max),
A.path
+ N'->'
+ RTRIM(B.orderid) + N'.' + B.state
),
state_count = A.state_count + 1,
A.start_lineID, A.start_state,
current_lineID = B.lineID,
current_state = B.state,
current_orderid = B.orderid,
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.current_orderid + A.flag = B.orderid
UNION ALL
-- 不同 LineID
SELECT
path = CONVERT(nvarchar(max),
A.path + N')->'
+ RTRIM(B.lineID) + N'{'
+ RTRIM(B.orderid) + N'.' + B.state
),
state_count = A.state_count + 1,
A.start_lineID, A.start_state,
current_lineID = B.lineID,
current_state = B.state,
current_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
-- 不同 LineID 的第1站正向
SELECT
path = CONVERT(nvarchar(max),
A.path
+ N'->'
+ RTRIM(B.orderid) + N'.' + B.state
),
state_count = A.state_count + 1,
A.start_lineID, A.start_state,
current_lineID = B.lineID,
current_state = B.state,
current_orderid = B.orderid,
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.current_orderid + 1 = B.orderid
UNION ALL
-- 不同 LineID 的第1站反向
SELECT
path = CONVERT(nvarchar(max),
A.path
+ N'->'
+ RTRIM(B.orderid) + N'.' + B.state
),
state_count = A.state_count + 1,
A.start_lineID, A.start_state,
current_lineID = B.lineID,
current_state = B.state,
current_orderid = B.orderid,
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.current_orderid - 1 = B.orderid
SET @rows = @rows + @@ROWCOUNT
END
SELECT
-- *,
path = path + N'}',
state_count
FROM @re
WHERE flag = 0
結果(數字5,7是要經過多少站:
3{1.廣州東-> 2.體育西-> 3.珠江新城-> 4.客村)-> 2{5.客村-> 4.中大} 5
1{1.廣州東-> 2.體育中心-> 3.體育西)-> 3{2.體育西-> 3.珠江新城-> 4.客村)-> 2{5.客村-> 4.中大} 7
