Java 五门科目中的一门必须添加到4个核心科目中。因此，要加在一起的列总数将为6列。我的问题是如何从五个等级中选出最好的两个，这就是为什么我使用表格样本@krokodilko +---------+--------+--------+--------+------

五门科目中的一门必须添加到4个核心科目中。因此，要加在一起的列总数将为6列。我的问题是如何从五个等级中选出最好的两个，这就是为什么我使用表格样本@krokodilko

+---------+--------+--------+--------+--------+--------+--------+--------+--------+----------+
|  Name   | Grade1 | G1_Pos | Grade2 | G2_Pos | Grade3 | G3_Pos | Grade4 | Grade5 | Agregate |
+---------+--------+--------+--------+--------+--------+--------+--------+--------+----------+
|  james  |    4   | 3rd    |     6  | 4th    |    1   | 1st    |     3  |      2 |          |
|  Mavis  |    1   | 1st    |     1  | 1st    |    3   | 3rd    |     2  |      3 |          |
|  john   |    5   | 4th    |     3  | 2nd    |    4   | 4th    |     4  |      4 |          |
|  bendo  |    2   | 2nd    |     5  | 3rd    |    2   | 2nd    |     1  |      2 |          |
+---------+--------+--------+--------+--------+--------+--------+--------+--------+----------+

String sql = "update jhs1 set Agregate=(SELECT SUM(Grade4+Grade5) AS ST) WHERE ID = jhs1.ID";
pst = conn.prepareStatement(sql);
pst.execute();

+---------+--------+--------+--------+--------+--------+--------+--------+--------+----------+
|  Name   | Grade1 | G1_Pos | Grade2 | G2_Pos | Grade3 | G3_Pos | Grade4 | Grade5 | Agregate |
+---------+--------+--------+--------+--------+--------+--------+--------+--------+----------+
|  james  |    4   | 3rd    |     6  | 4th    |    1   | 1st    |     3  |      2 |      10  |
|  Mavis  |    1   | 1st    |     1  | 1st    |    3   | 3rd    |     2  |      3 |       7  |
|  john   |    5   | 4th    |     3  | 2nd    |    4   | 4th    |     4  |      4 |      15  |
|  bendo  |    2   | 2nd    |     5  | 3rd    |    2   | 2nd    |     1  |      2 |       7  |
+---------+--------+--------+--------+--------+--------+--------+--------+--------+----------+

SELECT grade1+grade2+grade3 - least( grade1, grade2, grade3 )
FROM .....

SELECT grade1+grade2+grade3 -
       CASE greatest( G1_Pos , G2_Pos , G3_Pos )
          WHEN G1_Pos THEN Grade1
          WHEN G2_Pos THEN grade2
          WHEN G3_Pos THEN grade3
       END
FROM .....

+--------+---------+--------+--------+--------+--------+
| G1_Pos |  grade1 | G2_Pos | grade2 | G2_Pos | grade3 |
+--------+---------+--------+--------+--------+--------+
| 3rd    |      10 | 3rd    |      5 | 3rd    |     2  |
+--------+---------+--------+--------+--------+--------+