技術標籤：mysqlmysql演算法

Mysql刷題筆記

-- 0107 求出誰擁有最多的好友和他擁有的好友數目

CREATE TABLE T0107 
(
	requester_id INT,
	accepter_id INT,
	accept_date DATE
);

INSERT INTO T0107 VALUES (1,2,'2016-6-3');
INSERT INTO T0107 VALUES (1,3,'2016-6-8');
INSERT INTO T0107 VALUES (2,3,'2016-6-8');
INSERT INTO T0107 VALUES (3,4,'2016-6-9'
 
);

T0107
+--------------+-------------+-------------+
| requester_id | accepter_id | accept_date |
+--------------+-------------+-------------+
|            1 |           2 | 2016-06-03  |
|            1 |           3 | 2016-06-08  |
|            2 |           3 | 2016-06-08  |
|            3 |           4 | 2016
 
-06-09  |
+--------------+-------------+-------------+

結果
+------+-----+
| ID   | num |
+------+-----+
|    3 |   3 |
+------+-----+

SELECT ID,COUNT(*) AS num
FROM
(
  SELECT requester_id AS ID FROM T0107
	UNION ALL
	SELECT accepter_id AS ID FROM T0107
)t
GROUP BY ID
ORDER BY num DESC LIMIT 1