[Database] MYSQL Use - Character Set

A character set

1. Character set at what time can play a role?
   Time to save the data needs to use the character set
   data transmission, you also need to use the character set
   the character set when subsisting
   on the MySQL server, in the database, in the use of the table, in field is set
   on.
   when the server is installed, you can specify the default character set
2. Common character sets
   ASCII: Based on a Roman alphabet character set, which uses low 7 1 byte indicates that the word
   character, the high is always 0.
   LATIN1: relative to the ASCII character set to do the expansion, still use one byte character,
   but enable high, it extends the range represents the character set.
   GB2312: Simplified Chinese characters, a character take up to two bytes
   GB: just all the Chinese characters, a character take up to two bytes
   UTF8: international universal coding, a character take up to three bytes
   UTF8MB4: international universal coding, strengthen the identification of new text on the basis of utf8 on a
   take up to four bytes of characters

/* gbk字符集最大字符串长度: 65535/2 -1 */
create table test(
    text varchar(32766)
) charset=gbk;
/* utf8字符集最大字符串长度: 65535/3 -1 */
create table test1(
    text varchar(21844)
) charset=utf8;
/* utf8mb4字符集最大字符串长度: 65535/4 -1 */
create table test4(
    text varchar(16382)
) charset=utf8mb4;

3. View the current system mysql character set support

mysql> show variables like 'character_%';
/* 输出:
+--------------------------+------------+
| Variable_name           | Value     |
+--------------------------+------------+
| character_set_client     | utf8mb4   | 客户端来源数据使
用的字符集
| character_set_connection | utf8mb4   | 连接层字符集
| character_set_database   | utf8mb4   | 当前选中的数据库
的默认字符集
| character_set_filesystem | binary     | 文件系统字符集
| character_set_results   | utf8mb4   | 查询结果使用的字
符集
| character_set_server     | utf8mb4   | 默认的内部操作字
符集
| character_set_system     | utf8       | 系统元数据(字段
名、表名等)的字符集
| character_sets_dir       | /usr/lo... |
+--------------------------+------------+
*/

4. Modify the character set encoding of the current system mysql

• All changes

set names gbk;

• Specified modification

set character_set_client = gbk;
set character_set_results = gbk;