移动设备 表情符号的数据库存储 与 utf8 与utf8mb4 字符集

mysql>  SHOW VARIABLES WHERE Variable_name LIKE ‘character\_set\_%‘ OR Variable_name LIKE ‘collation%‘;
+--------------------------+-----------------+
| Variable_name            | Value           |
+--------------------------+-----------------+
| character_set_client     | utf8            |
| character_set_connection | utf8            |
| character_set_database   | utf8            |
| character_set_filesystem | binary          |
| character_set_results    | utf8            |
| character_set_server     | utf8            |
| character_set_system     | utf8            |
| collation_connection     | utf8_general_ci |
| collation_database       | utf8_general_ci |
| collation_server         | utf8_general_ci |
+--------------------------+-----------------+
10 rows in set (0.20 sec)

mysql> SET character_set_client = gbk;
Query OK, 0 rows affected (0.31 sec)

mysql> SET character_set_connection=gbk ;
Query OK, 0 rows affected (0.00 sec)

mysql> set character_set_database=utf8mb4;
Query OK, 0 rows affected (0.00 sec)

mysql> set character_set_filesystem=binary;
Query OK, 0 rows affected (0.00 sec)


mysql> set character_set_results=gbk;
Query OK, 0 rows affected (0.00 sec)

  mysql> set character_set_system=utf8;
  ERROR 1238 (HY000): Variable ‘character_set_system‘ is a read only variable

mysql> set names gbk;

它相当于下面的三句指令：
SET character_set_client = gbk;
SET character_set_results = gbk;
SET character_set_connection = gbk;

SET NAMES ‘charset_name‘ COLLATE ‘collation_name‘

[client]     //通过连接器连接 EG：PHP


[mysql]      //mysql程序登陆时的字符集

      default-character-set    = gbk
//等价
--SET character_set_client     = gbk;
--SET character_set_results    = gbk;
--SET character_set_connection = gbk;

#character_set_system=utf8mb4
#character_set_client=utf8mb4
#character_set_connection=utf8mb4
#character_set_database=utf8mb4
#character_set_results=utf8mb4      // #代表相应变量不能设置在这个区中,报错,mysql登陆报错

[mysqld]   //mysqld起动时设置字符集

character_set_filesystem=binary
character-set-server=utf8mb4

collation-server = utf8mb4_unicode_ci
init_connect=‘set autocommit=0; set names gbk;‘   //root 用户不会执行

#character_set_system=utf8mb4
#character_set_client=utf8mb4 
#character_set_connection=utf8mb4 //#代表相应变量不能设置在这个区中，mysqld 起动报错
#character_set_database=utf8mb4 
#character_set_results=utf8mb4

[]

mysql> select * from t1;
+------------+-----------------+---------------------+
| cur_user   | n_user          | in_time             |
+------------+-----------------+---------------------+
| @localhost | mysql@localhost | 2016-07-05 00:25:02 |
+------------+-----------------+---------------------+
1 row in set (0.19 sec)


mysql> ALTER TABLE t1 MODIFY cur_user CHAR(50) CHARACTER SET sjis;  

mysql> show create table t1;
   CREATE TABLE `t1` (
  `cur_user` char(50) CHARACTER SET sjis DEFAULT NULL,
  `n_user`  varchar(100) CHARACTER SET utf8 DEFAULT NULL,
  `in_time` timestamp NULL DEFAULT CURRENT_TIMESTAMP
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4