insert into A（C1,C2） select * from (select C1,C2 from B limit 10) r

------解决方案--------------------
INSERT INTO A SELECT * FROM (SELECT C1,C2 FROM B limit 10)t;


------解决方案--------------------
mysql> select * from tb_1;
+------+--------+----------+
| id   | userid | friendid |
+------+--------+----------+
|    0 |      1 |        3 |
|    1 |      1 |        4 |
|    2 |      2 |        3 |
|    3 |      2 |        6 |
|    4 |      3 |        5 |
|    5 |      3 |        6 |
|    6 |      4 |        5 |
|    7 |      4 |        2 |
|    8 |      5 |        2 |
|    9 |      5 |        7 |
|   10 |      6 |        7 |
|   11 |      6 |        8 |
+------+--------+----------+
12 rows in set (0.04 sec)

mysql> create table tb_2 like tb_1;
Query OK, 0 rows affected (0.18 sec)

mysql> insert into tb_2 select * from tb_1 limit 5;
Query OK, 5 rows affected (0.05 sec)
Records: 5  Duplicates: 0  Warnings: 0

我这个是可以的。