SQL代码不适用于查找最小公倍数值，但相反（找到最常见的值）

Question

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

我试图找到在某列中出现次数最少的值。当我运行这段代码时，它不会返回任何结果，但是当我做相反的操作时（count(*) >= ALL），它会起作用，并为我提供发生次数最多的值。为什么会这样？

Answer 1

我认为你缺少一个group by：

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

如果我使用这种风格，我还是会倾向于写：

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

两个版本做同样的事情。