mysql ORDER results按列數發生次數

Question

我有一個數據庫，它將收到大量的信息，但最重要的是它會收到每行的城市名稱。下面的示例：

id   city 
1   London 
2   Manchester 
3   London 
4   Brighton 
5   Oxford 
6   Oxford 
7   London 

我想從此表中只選擇城市名稱，顯示最常出現的前3名結果。

到目前爲止，我使用下面，我發現查詢：

SELECT N.city, COUNT(*) AS howmany 
FROM (SELECT DISTINCT city FROM events) AS N, 
events AS T 
WHERE N.city = T.city 
GROUP BY N.city 
ORDER BY howmany 
LIMIT 0,2 

Answer 1

您可以簡化現有的查詢到一個單一的訪問事件表，而不需要將它加入到自己：

SELECT N.city, 
     COUNT(N.city) AS howmany 
    FROM events AS N 
GROUP BY N.city 
ORDER BY howmany 
LIMIT 3 

，如果你不想要回數，請嘗試：

SELECT N.city 
    FROM events AS N 
GROUP BY N.city 
ORDER BY COUNT(N.city) 
LIMIT 3 

Answer 2

你不需要additi加入GROUP BY已經爲您處理DISTINCT方面。

SELECT city, COUNT(*) AS howmany 
FROM 
events 
GROUP BY city 
ORDER BY howmany DESC 
LIMIT 0,3 

Answer 3

如果你只是想在你的最終結果的「城市」字段：

SELECT city FROM (
    SELECT city, COUNT(*) as ccount 
    FROM events 
    GROUP BY city 
) 
ORDER BY ccount DESC 
LIMIT 3 

如果你不關心最終結果的字段，只要城市是一個它更簡單：

SELECT city, COUNT(*) as ccount 
FROM events 
GROUP BY city 
ORDER BY ccount DESC 
LIMIT 3