数学建模关于加工排序的问题~~急急急

Question

[有四个工件等待在同一台机器上加工，若加工的先后次序可以任意，各工件之间的调整时间如下表：
到A 到B 到C 到D
从A － 15 20 5
从B 30 － 30 15
从C 25 25 － 15
从D 20 35 10 －
试确定最佳加工顺序。

Answer 1

SQL> SELECT * FROM test;
 
HEAD A_TIME B_TIME C_TIME D_TIME
---- ------ ------ ------ ------
A               15     20      5
B        30            30     15
C        25     25            15
D        20     35     10 
 
SQL> 
SQL> select * from test1;
SQL> select * from test;
 
HEAD A_TIME B_TIME C_TIME D_TIME
---- ------ ------ ------ ------
A               15     20      5
B        30            30     15
C        25     25            15
D        20     35     10 
 
SQL> select * from test1;
 
FIRST SECOND COST_ALL
----- ------ --------
B     A            30
C     A            25
D     A            20
A     B            15
C     B            25
D     B            35
A     C            20
B     C            30
D     C            10
A     D             5
B     D            15
C     D            15
 
12 rows selected
 
SQL> 
SQL> SELECT a.first,a.second,b.second third,c.second forth,SUM(a.cost_all+b.cost_all+c.cost_all) FROM test1 a,test1 b,test1 c
  2  WHERE a.second=b.first AND b.second=c.first
  3    AND a.first<>b.second AND a.first<>c.second
  4    AND b.first<>c.second
  5  GROUP BY a.first,a.second,b.second ,c.second
  6  ORDER BY SUM(a.cost_all+b.cost_all+c.cost_all) ASC;
 
FIRST SECOND THIRD FORTH SUM(A.COST_ALL+B.COST_ALL+C.CO
----- ------ ----- ----- ------------------------------
A     B      D     C                                 40
A     D      C     B                                 40
B     A      D     C                                 45
B     D      C     A                                 50
C     D      A     B                                 50
D     C      A     B                                 50
B     D      A     C                                 55
C     A      B     D                                 55
C     B      D     A                                 60
A     B      C     D                                 60
B     C      A     D                                 60
A     C      B     D                                 60
C     B      A     D                                 60
D     A      B     C                                 65
D     A      C     B                                 65
B     A      C     D                                 65
C     A      D     B                                 65
D     C      B     A                                 65
B     C      D     A                                 65
A     C      D     B                                 70
 
FIRST SECOND THIRD FORTH SUM(A.COST_ALL+B.COST_ALL+C.CO
----- ------ ----- ----- ------------------------------
A     D      B     C                                 70
C     D      B     A                                 80
D     B      A     C                                 85
D     B      C     A                                 90
 
24 rows selected
 
SQL>
所以最佳加工顺寻是
1 A B D C 40
2 A D C B 40
消耗时间都是40分钟

Answer 2

产生test1的语句
INSERT INTO test1
SELECT head,'A',A_time FROM test WHERE A_TIME IS NOT NULL
UNION ALL 
SELECT head,'B',B_time FROM test WHERE B_TIME IS NOT NULL
UNION ALL 
SELECT head,'C',C_time FROM test WHERE C_TIME IS NOT NULL
UNION ALL 
SELECT head,'D',D_time FROM test WHERE D_TIME IS NOT NULL;