如何在mysql中使用group_concat

GROUP_CONCAT([DISTINCT] expr [,expr ...]
             [ORDER BY {unsigned_integer | col_name | expr}
                 [ASC | DESC] [,col_name ...]]
             [SEPARATOR str_val])

+----+-------+---------+
| id | name  | subject |
+----+-------+---------+
| 1  | Alice | Math    |
| 2  | Bob   | English |
| 3  | Alice | Science |
| 4  | Bob   | Math    |
+----+-------+---------+

SELECT name, GROUP_CONCAT(subject) AS subjects
FROM students
GROUP BY name;

+-------+-------------------+
| name  | subjects          |
+-------+-------------------+
| Alice | Math,Science      |
| Bob   | English,Math      |
+-------+-------------------+