Question

我们说我有这张桌子：

+----+------+---------+
| Id | Item | Country |
+----+------+---------+
|  1 | b123 | Austria |
|  2 | a123 | Italy   |
|  3 | b990 | Germany |
|  4 | h231 | Austria |
|  5 | y233 | France  |
|  6 | u223 | Austria |
|  7 | p022 | Spain   |
|  8 | d133 | Italy   |
|  9 | w112 | Germany |
| 10 | j991 | Austria |
+----+------+---------+

我想在该表上执行SELECT并订购Country最重复的结果。所以预期的输出应该是：

+----+------+---------+
| Id | Item | Country |
+----+------+---------+
|  1 | b123 | Austria |
|  4 | h231 | Austria |
|  6 | u223 | Austria |
| 10 | j991 | Austria |
|  2 | a123 | Italy   |
|  8 | d133 | Italy   |
|  3 | b990 | Germany |
|  9 | w112 | Germany |
|  5 | y233 | France  |
|  7 | p022 | Spain   |
+----+------+---------+

我该怎么做？

我试过这个：

SELECT * FROM items WHERE Item != '' GROUP BY Item HAVING COUNT(*) > 1 ORDER BY COUNT(*) DESC

但是会返回这样的东西：

+----+------+---------+
| Id | Item | Country |
+----+------+---------+
|  1 | b123 | Austria |
|  8 | d133 | Italy   |
|  3 | b990 | Germany |
|  5 | y233 | France  |
|  7 | p022 | Spain   |
+----+------+---------+

Answer 1

A - Original table
B - Getting the counts at Country Level.

通过加入A和B，我们可以按照计数的降序对数据进行排序，并显示表格中的所有项目。

SELECT A.*
  FROM items A
INNER JOIN 
(    SELECT Country,COUNT(*) AS cnt       
      FROM items 
     WHERE Item != '' 
     GROUP BY Item 
) B
   ON A.Country = B.Country
ORDER BY B.cnt DESC,A.Country,A.Id;

Answer 2

您可以在order by中添加子查询。所以一种方法是：

select i.*
from items i
where i.item <> ''
order by (select count(*) from items i2 where i2.item = i.item) desc;

与执行group by并加入值

相比，这种方法有优点和缺点

优势：它可以利用items(item)上的索引。
优点：如果where子句具有高度选择性，则每行只调用一次子查询。
缺点：如果where子句的选择性不高，则每行只调用一次子查询。

Mysql：按值频率排序行

2 个答案: