平均值形式列 - MySQL的

Question

我有這個表：

+----+---------+------+----------+ 
| ID | ID_USER | NOTE | QUESTION | 
+----+---------+------+----------+ 
| 1 | 12 | 3 |  1 | 
| 2 | 31 | 2 |  1 | 
| 3 | 12 | 9 |  1 | 
| 4 | 31 | 8 |  2 | 
| 5 | 12 | 10 |  2 | 
| 6 | 31 | 3 |  2 | 
+----+---------+------+----------+ 

如何通過ID_USER，問題出口值將它們分組，使票據的平均？值分組如下表所示：

+----+----------+---------+-------------+ 
| ID | QUESTION | ID_USER | MEDIUM_NOTE | 
+----+----------+---------+-------------+ 
| 1 |  1 | 12 |  6  | 
| 2 |  1 | 31 |  2  | 
| 3 |  2 | 12 |  10 | 
| 4 |  2 | 31 |  5.5 | 
+----+----------+---------+-------------+ 

謝謝！

Answer 1

SELECT 
    id_user, 
    question, 
    AVG(note) AS medium_note 
FROM notes 
GROUP BY id_user, question 

您可以按用戶和問題分組，然後計算平均值。

Example

Answer 2

假設id列是獨一無二的：

SELECT id,question,id_user,avg(note) as 'MEDIUM_NOTE' FROM table_name GROUP BY id_user,question ORDER BY id;