在没有重新查询的情况下访问另一个表中的查询计数记录？

Question

我正在尝试制作一份报告，我需要知道像这样的另一个表中的项目数

+----------+--------+--------------------------------------------+
| Sale No. | Widget |                 Total Sold                 |
+----------+--------+--------------------------------------------+
|      123 | foo    | Dcount(another table where widget = "foo") |
|      456 | bar    | Dcount(another table where widget = "bar") |
+----------+--------+--------------------------------------------+

。

SELECT  [Sale No.]
        , Widget
        , Dcount("SELECT foo from whatever where widget = " & widget) as [Total Sold]
FROM    sometable

不幸的是，这会查询数据库中的每条记录，对于这样一个必须每天运行的报告来说，这并不是很有效。

有没有办法查询一次，通过 VBA 或一些我不知道的 SQL 将查询保存在内存中或每个唯一项目的计数。基本上只查询另一张表一次而不是N次。

---

这是一个更准确的表格，可以更准确地反映我的数据

+----------+------------+---------+------------------+
| Employee | Department | Policy  | Review Requested |
+----------+------------+---------+------------------+
|      123 | Sales      | PlanABC | TRUE             |
|      456 | Sales      | PlanABC | TRUE             |
|      789 | Accounting | PlanXYZ | FALSE            |
|   101112 | Accounting | PlanXYZ | TRUE             |
|   131415 | Sales      | PlanXYZ | FALSE            |
|   161718 | Admin      | PlanJKL | TRUE             |
+----------+------------+---------+------------------+

我想要的结果

+------------+----------+---------+----------------------+
| Department | Employee | Policy  | Count of All Polices |
+------------+----------+---------+----------------------+
| Sales      |      123 | PlanABC |                    2 |
| Sales      |      456 | PlanABC |                    2 |
| Accounting |   101112 | PlanXYZ |                    3 |
| Admin      |   161718 | PlanJKL |                    1 |
+------------+----------+---------+----------------------+

Answer 1

如果你的表设置如下：

| Sale No | Widget |
|---------|--------|
| 1       | Foo    |
| 2       | Bar    |
| 3       | Foo    |
| 4       | Foo    |
| 5       | Bar    |
| 6       | Foo    |
| 7       | Foo    |
| 8       | Bar    |
| 9       | Bar    |
| 10      | Foo    |

您不能包含Sale No，因为它会将值分组。

 SELECT     Widget
            , COUNT(Widget) AS [Total Sold]    
 FROM       sometable
 GROUP BY   Widget  

只需添加小部件并对其进行分组即可返回：

| Widget | Total Sold |
|--------|------------|
| Bar    | 4          |
| Foo    | 6          |  

另一方面，如果您的 Sale No 字段重复，那么您可以获得每个 Sale No 的计数。

| Sale No | Widget |
|---------|--------|
| 1       | Foo    |
| 1       | Bar    |
| 5       | Foo    |
| 5       | Foo    |
| 5       | Bar    |
| 7       | Foo    |
| 7       | Foo    |
| 7       | Bar    |
| 7       | Bar    |
| 10      | Foo    |  

这里添加了Sale No，查询按所有未聚合的字段分组。

 SELECT     [Sale No]
            , Widget
            , COUNT(Widget) As [Total Sold]
 FROM       sometable
 GROUP BY   [Sale No]
            , Widget  

这将返回这个表：

| Sale No | Widget | Total Sold |
|---------|--------|------------|
| 1       | Bar    | 1          |
| 1       | Foo    | 1          |
| 5       | Bar    | 1          |
| 5       | Foo    | 2          |
| 7       | Bar    | 2          |
| 7       | Foo    | 2          |
| 10      | Foo    | 1          |

编辑：
根据提供的表，此 SQL 应该给出正确的结果：

SELECT      T1.Department
            , T1.Employee
            , T1.Policy
            , COUNT(T2.Policy)
FROM        sometable T1 INNER JOIN sometable T2 ON T1.Policy = T2.Policy
GROUP BY    T1.Department
            , T1.Employee
            , T1.Policy  

结果表：

| Department | Employee | Policy  | Expr1003 |
|------------|----------|---------|----------|
| Accounting | 789      | PlanXYZ | 3        |
| Accounting | 101112   | PLanXYZ | 3        |
| Admin      | 161718   | PLanJKL | 1        |
| Sales      | 123      | PlanABC | 1        |
| Sales      | 456      | PalnABC | 1        |
| Sales      | 131415   | PlanXYZ | 3        |