SQL代碼不適用於查找最小公倍數值，但相反（找到最常見的值）

Question

SELECT `suburbcode` 
    FROM PROPERTY 
    HAVING count(*) <= 
    ALL(SELECT count(*) 
     FROM PROPERTY 
     GROUP BY `suburbcode`) 

我試圖找到在某列中出現次數最少的值。當我運行這段代碼時，它不會返回任何結果，但是當我做相反的操作時（count(*) >= ALL），它會起作用，併爲我提供發生次數最多的值。爲什麼會這樣？

Answer 1

我認爲你缺少一個group by：

SELECT suburbcode 
FROM PROPERTY 
GROUP BY suburbcode 
HAVING count(*) <= ALL (SELECT count(*) 
         FROM PROPERTY 
         GROUP BY `suburbcode` 
         ); 

如果我使用這種風格，我還是會傾向於寫：

SELECT suburbcode 
FROM PROPERTY 
GROUP BY suburbcode 
HAVING count(*) <= (SELECT count(*) 
        FROM PROPERTY 
        GROUP BY `suburbcode` 
        ORDER BY count(*) DESC 
        LIMIT 1 
        ); 

兩個版本做同樣的事情。