使用 SQL 显示来自四个表的数据

Question

四个Table

我有四个表，即 Candidates、Parties、Multiplier 和 Votes。

Table 带有示例的布局

表格布局如下：

• 候选人

例如

+--------------+----------+----------------+--------+
| Candidate_ID | Surname  |      Name      | Gender |
+--------------+----------+----------------+--------+
|            1 | BAREND   | INNOCK CHARLIE | MALE   |
|            2 | DU PREEZ | DONAVAN GARY   | MALE   |
|            3 | BERTELS  | MEGAN MARIÉ    | FEMALE |
|            4 | HOPLEY   | CAITLIN TAYLOR | FEMALE |
+--------------+----------+----------------+--------+

• 派对

例如

+----------+------------+-------+-------+
| Party_ID | Party_Type | Grade | Class |
+----------+------------+-------+-------+
| H1       | Head       |       |       |
| T1       | TEACHER    |       |       |
| 8N       | LEARNER    |     8 | N     |
| 9N       | LEARNER    |     9 | N     |
| 10N      | LEARNER    |    10 | N     |
| 11N      | LEARNER    |    11 | N     |
+----------+------------+-------+-------+

注意：N 介于 A 和 J 之间，例如8A, 8B, 8C … 8J.

• 乘数

例如

+------------+------------+
| Party_Type | Multiplier |
+------------+------------+
| HEAD       |          3 |
| TEACHER    |          2 |
| LEARNER    |          1 |
+------------+------------+

• 票数：A类是对管理委员会职位的投票，B类是对副手的投票，C类是对主席的投票，例如头女孩或男孩。

例如

+--------------+----------+--------+--------+--------+
| Candidate_ID | Party_ID | ClassA | ClassB | ClassC |
+--------------+----------+--------+--------+--------+
|            1 | H1       |      2 |      2 |      1 |
|            4 | 8C       |     23 |      5 |      2 |
|            2 | H1       |      3 |      2 |      2 |
|            3 | 9D       |     30 |     16 |     10 |
|            1 | T1       |     15 |      7 |      5 |
|            3 | T1       |     17 |     10 |      9 |
|            4 | T1       |      4 |      2 |      1 |
|            2 | 10E      |     24 |     10 |      4 |
+--------------+----------+--------+--------+--------+

基本上，我正在尝试编写一个 SQL 语句来计算每个候选人的所有选票，然后根据选票从多到少对记录进行排序，如下所示：

+----+----------+----------------+--------+--------+--------+
| ID | Surname  |     Names      | ClassA | ClassB | ClassC |
+----+----------+----------------+--------+--------+--------+
|  3 | BERTELS  | MEGAN MARIÉ    |     96 |     36 |     28 |
|  4 | HOPLEY   | CAITLIN TAYLOR |     64 |     19 |      8 |
|  1 | BAREND   | INNOCK CHARLIE |     36 |     20 |     13 |
|  2 | DU PREEZ | DONAVAN GARY   |     33 |     16 |     10 |
+----+----------+----------------+--------+--------+--------+

我的努力

到目前为止，我只能在不使用乘数的情况下统计所有选票：

SELECT C.Candidate_ID, C.Surname, C.Name, Sum(V.ClassA) AS ClassA, Sum(V.ClassB) AS ClassB, Sum(V.ClassC) AS ClassC
FROM Candidates C INNER JOIN Votes V ON C.Candidate_ID = V.Candidate_ID
GROUP BY C.Candidate_ID, C.Surname, C.Name;

我的问题

所以我相信我的问题很清楚：我需要根据选票来自的政党类型分别应用乘数。

Answer 1

我认为应该这样做：

SELECT 
  C.Candidate_ID,
  C.Surname, 
  C.Name, 
  SUM(V.ClassA * M.Multiplier) AS ClassA, 
  SUM(V.ClassB * M.Multiplier) AS ClassB, 
  SUM(V.ClassC * M.Multiplier) AS ClassC
FROM 
  ( ( Candidates C 
      INNER JOIN Votes V ON C.Candidate_ID = V.Candidate_ID )
    INNER JOIN Parties P ON V.Party_ID = P.Party_ID )
  INNER JOIN Multiplier M ON P.Party_Type = M.Party_Type
GROUP BY 
  C.Candidate_ID, 
  C.Surname, 
  C.Name;