mysql同一表记录某一字段内容合并

mysql> create table t(id int,name varchar(20));
Query OK, 0 rows affected (0.09 sec)
mysql> insert into t values (1,'aa'),(1,'bb'),(2,'cc'),(2,'dd');
Query OK, 4 rows affected (0.00 sec)
Records: 4  Duplicates: 0  Warnings: 0
mysql> commit;
Query OK, 0 rows affected (0.00 sec)
mysql> select * from t;
+------+------+
| id   | name |
+------+------+
|    1 | aa   |
|    1 | bb   |
|    2 | cc   |
|    2 | dd   |
+------+------+
4 rows in set (0.01 sec)
mysql> select id,GROUP_CONCAT(name) from t group by id;
+------+--------------------+
| id   | GROUP_CONCAT(name) |
+------+--------------------+
|    1 | aa,bb              |
|    2 | cc,dd              |
+------+--------------------+
2 rows in set (0.00 sec)