sql - 如何使用 group by 子句从 MS Access 表中获取计数？

Question

我对这个 SQL 查询彻底崩溃了，我希望有人能对我应该做的事情有所启发。

我有以下表格，它们由“anumber”链接；

athletes
--------
anumber     (id)
acountry    ('Australia','Japan')
aname

result_placing
--------------
result_id       id
anumber         (id linked to athletes)
result_placing  (Gold, Silver or null)

我想获得与多少金、银结果相关的国家列表。所以输出如下：

country     | resul_placing | result_count
----------- | ------------- | ------------
Australia   | Gold          |       2
Australia   | Silver        |       1

我试过这样的事情：

SELECT      acountry 
FROM        athletes 
INNER JOIN  result_placing 
ON          athletes.anumber = result_placing.anumber

这表明

 Australia | Gold   |
 Australia | Silver |

只是不确定如何获得每个的计数。我试过 count(distinct) 但 Access 不喜欢它。

一旦我在其中使用 Count ，就像：

SELECT      a.acountry
        ,   r.placing
        ,   count(a.acountry) 
FROM        athlete         a 
INNER JOIN  result_place    r 
ON          a.anumber       = r.anumber

我收到：

You tried to execute a query that does not include the specified expression 'acountry' as part of an aggregate function

Answer 1

尝试

SELECT      a.acountry
        ,   r.result_placing
        ,   sum(*) as cnt 
FROM        athletes        a 
RIGHT JOIN  result_placing  r 
ON          a.anumber       = r.anumber 
GROUP BY    a.acountry
        ,   r.result_placing 
ORDER BY    a.acountry

Answer 2

没有试过这个，但这里有。您需要使用分组依据。请尝试以下查询

SELECT a.acountry, r.result_placing, count(a.acountry) FROM athletes a INNER JOIN     result_placing r ON a.anumber = r.anumber group by a.acountry, r.result_placing

Answer 3

这是使用LEFT OUTER JOIN和GROUP BY查询数据的一种方法。

Script：

SELECT              a.acountry
                ,   IIf(r.result_placing = '' 
                        OR IsNull(r.result_placing), 
                        'n/a', 
                        r.result_placing
                    ) AS medal
                ,   COUNT(r.result_id) AS medalcount
FROM                athletes a
LEFT OUTER JOIN     result_placing r
ON                  a.anumber = r.anumber
GROUP BY            a.acountry
                ,   r.result_placing

Table Data：

运动员表数据

results_placing表数据

Output：

查询输出