在 MySQL 中一起使用 Distinct、Count 和 Group

Question

我有一个 'attractions' 的数据库 table，每个景点都有县 and/or 市的列。我需要按字母顺序显示一个县市列表，以及每个县市的记录总数。

下面的 SQL 查询工作正常，除了 COUNT 只显示每个景点的总数，而不是每个县或市的景点总数。

谁能告诉我如何将下面的两个 SQL 语句组合在一起？

SQL:

   SELECT entry, COUNT(entry) AS totalForEntry 
   FROM ( SELECT DISTINCT county AS entry
          FROM venues 
          WHERE (county  IS NOT NULL AND county <> '' ) 

          UNION ALL 

          SELECT DISTINCT city as entry
          FROM venues
          WHERE (city IS NOT NULL 
                 AND
                 city  <> ''  
                 )
      ) X GROUP BY entry ORDER BY entry ASC

结果：

Hove (1)
Inverness-shire (1)
Isle of Man (1)
Kent (1)
Lancashire (1)
Leeds (1)
Leicester (1)
Leicestershire (2)
Lincolnshire (1)
Liverpool (1)

以下计算县的工作，我也需要它来计算城市并将其与上面的查询结合起来：

SELECT DISTINCT county, COUNT(county) AS Count
FROM venues
WHERE (county IS NOT NULL AND county <> '') 
GROUP BY county ORDER BY county ASC

正确的结果应该是这样的：

Hove (7)
Inverness-shire (3)
Isle of Man (12)
Kent (20)
Lancashire (34)
Leeds (31)
Leicester (5)
Leicestershire (53)
Lincolnshire (7)
Liverpool (43)

非常感谢。

Answer 1

将 DISTINCT 与 GROUP BY 一起使用没有意义。你可以这样做：

SELECT county AS entry, COUNT(county) AS Count
FROM venues
WHERE (county IS NOT NULL AND county <> '') 
GROUP BY county 

UNION ALL 

SELECT city as entry, COUNT(city) As Count
FROM venues
WHERE (city IS NOT NULL AND city  <> '')
GROUP BY city 
ORDER BY entry ASC

在 MySQL 中一起使用 Distinct、Count 和 Group

Using Distinct, Count and Group together in MySQL

mysql

count

distinct