数据库和表的 charset 分别是起什么作用的？为什么我能 insert 中文到 charset 是 latin1 的库和表？

如果 charset 不是对 insert 进行限制的，那是用在什么地方的？
测试过程如下：
mysql server 版本:
+-------------------------+---------------------+
| Variable_name           | Value               |
+-------------------------+---------------------+
| protocol_version        | 10                  |
| version                 | 5.1.73              |
| version_comment         | Source distribution |
| version_compile_machine | x86_64              |
| version_compile_os      | redhat-linux-gnu    |
+-------------------------+---------------------+


连接信息

mysql> SHOW SESSION VARIABLES LIKE 'character\_set\_%';
+--------------------------+--------+
| Variable_name            | Value  |
+--------------------------+--------+
| character_set_client     | latin1 |
| character_set_connection | latin1 |
| character_set_database   | latin1 |
| character_set_filesystem | binary |
| character_set_results    | latin1 |
| character_set_server     | latin1 |
| character_set_system     | utf8   |
+--------------------------+--------+
7 rows in set (0.00 sec)

mysql> SHOW SESSION VARIABLES LIKE 'collation\_%';
+----------------------+-------------------+
| Variable_name        | Value             |
+----------------------+-------------------+
| collation_connection | latin1_swedish_ci |
| collation_database   | latin1_swedish_ci |
| collation_server     | latin1_swedish_ci |
+----------------------+-------------------+
3 rows in set (0.00 sec)

测试的数据库和表信息：

mysql> show create database sunny_test;
+------------+-----------------------------------------------------------------------+
| Database   | Create Database                                                       |
+------------+-----------------------------------------------------------------------+
| sunny_test | CREATE DATABASE `sunny_test` /*!40100 DEFAULT CHARACTER SET latin1 */ |
+------------+-----------------------------------------------------------------------+

mysql> show create table pet;
+-------+------------------------------------------------------------------------------------------------------------------------------+
| Table | Create Table                                                                                                                 |
+-------+------------------------------------------------------------------------------------------------------------------------------+
| pet   | CREATE TABLE `pet` (
  `name` varchar(20) NOT NULL DEFAULT '',
  PRIMARY KEY (`name`)
) ENGINE=MyISAM DEFAULT CHARSET=latin1 |
+-------+------------------------------------------------------------------------------------------------------------------------------+
 
mysql> insert into pet values ("你好");
Query OK, 1 row affected (0.00 sec)

mysql> select * from pet;
+--------+
| name   |
+--------+
| 你好 |
+--------+
1 row in set (0.00 sec)


mysql> insert into pet values ("♥");
Query OK, 1 row affected (0.00 sec)

mysql> select * from pet;
+--------+
| name   |
+--------+
| ♥    |
| 你好 |
+--------+
2 rows in set (0.00 sec)
救救孩子