1, 修改数据库字符集：
ALTER DATABASE db_name DEFAULT CHARACTER SET character_name[COLLATE ...];
2，修改表和所有字符列（char,varchar,text）的字符集：
ALTER TABLE tb_name CONVERT TO CHARACTER SET character_name[COLLATE ...]
例如：ALTER TABLE users CONVERT TO CHARACTER SET utf8 COLLATE utf8_general_ci;
3，只修改表的默认字符集：
ALTER TABLE tb_name DEFAULT CHARACTER SET character_name[COLLATE ...];
例如：ALTER TABLE users DEFAULT CHARACTER SET utf8 COLLATE utf8_general_ci;
4，修改字段的字符集：
ALTER TABLE tb_name CHANGE c_name c_name CHARACTER SET character_name[COLLATE ...];
例如：ALTER TABLE users CHANGE nick nick VARCHAR(300) CHARACTER SET utf8 COLLATE utf8_general_ci;
5，查看数据库编码
SHOW CREATE DATABASE db_name;
6，查看表编码
SHOW CREATE TABLE tb_name;
7，查看字段编码
SHOW FULL COLUMNS FROM tb_name;