mysql組並計數兩列

Question

我不知道如何在一個表的兩列中對名稱進行分組和計數。 我的桌子的結構是這樣的：

+------+-------------------+
| user | friend1 | friend2 |
+------+---------+---------+
|user1 | Adam    | Filip   | 
|user2 | Boris   | Norbert |
|user3 | Filip   | Carol   |
|user4 | Carol   | Filip   |
|user5 | Boris   | Patricia|
+------+---------+---------+

我想得到的結果是：

+----------+---+
| Filip    | 3 |
| Boris    | 2 |
| Carol    | 2 |
| Adam     | 1 |
| Norbert  | 1 |
| Patricia | 1 |
+----------+---+

按計數排序。

我嘗試過這樣的事情：

SELECT friend1 AS friends, friend2 AS friends, COUNT(friends) AS friedscount FROM table GROUP BY friends ORDER BY friedscount DESC

Answer 1

首先使用UNION ALL合並行，以在子查詢中保留重復項，然后計數

SELECT  friend, COUNT(*) friedscount 
FROM
        (
            SELECT  friend1 AS friend FROM TableName UNION ALL
            SELECT  friend2 AS friend FROM TableName
        ) a
GROUP   BY  friend
ORDER BY friedscount DESC

這是一個演示