发布于 2016-03-12 06:36:00 | 330 次阅读 | 评论: 0 | 来源: 网友投递
Mysql关系型数据库管理系统
MySQL是一个开放源码的小型关联式数据库管理系统，开发者为瑞典MySQL AB公司。MySQL被广泛地应用在Internet上的中小型网站中。由于其体积小、速度快、总体拥有成本低，尤其是开放源码这一特点，许多中小型网站为了降低网站总体拥有成本而选择了MySQL作为网站数据库。
MySQL 需要支持 emoji 表情符号版本需要大于5.5.3，且字符集需要设置为utf8mb4 字符集。
utf8mb4和utf8到底有什么区别呢？原来以往的mysql的utf8一个字符最多3字节，而utf8mb4则扩展到一个字符最多能有4字节，所以能支持更多的字符集。
将Mysql的编码从utf8转换成utf8mb4。
需要 >= MySQL 5.5.3版本、从库也必须是5.5的了、低版本不支持这个字符集、复制报错
停止MySQL Server服务
修改 my.cnf或者mysql.ini
[client]
default-character-set = utf8mb4
[mysql]
default-character-set = utf8mb4
[mysqld]
character-set-client-handshake = FALSE
character-set-server = utf8mb4
collation-server = utf8mb4_unicode_ci
init_connect='SET NAMES utf8mb4'
重启 MySQL Server、检查字符集。
查看服务器字符集设置
mysql> SHOW VARIABLES WHERE Variable_name LIKE 'character%' OR Variable_name LIKE 'collation%';
+--------------------------+--------------------+
| Variable_name | Value |
+--------------------------+--------------------+
| character_set_client | utf8mb4 |
| character_set_connection | utf8mb4 |
| character_set_database | utf8mb4 |
| character_set_filesystem | binary |
| character_set_results | utf8mb4 |
| character_set_server | utf8mb4 |
| character_set_system | utf8 |
| collation_connection | utf8mb4_unicode_ci |
| collation_database | utf8mb4_unicode_ci |
| collation_server | utf8mb4_unicode_ci |
+--------------------------+--------------------+
查看数据库字符集
mysql> select * from SCHEMATA where SCHEMA_NAME='ttlsa';
+--------------+-------------+----------------------------+------------------------+----------+
| CATALOG_NAME | SCHEMA_NAME | DEFAULT_CHARACTER_SET_NAME | DEFAULT_COLLATION_NAME | SQL_PATH |
+--------------+-------------+----------------------------+------------------------+----------+
| def | ttlsa | utf8mb4 | utf8mb4_unicode_ci | NULL |
+--------------+-------------+----------------------------+------------------------+----------+
查看表字符集
mysql> select TABLE_SCHEMA,TABLE_NAME,TABLE_COLLATION from information_schema.TABLES;
+--------------------+----------------------------------------------------+--------------------+
| TABLE_SCHEMA | TABLE_NAME | TABLE_COLLATION |
+--------------------+----------------------------------------------------+--------------------+
查看列字符集
mysql> select TABLE_SCHEMA,TABLE_NAME,COLUMN_NAME,COLLATION_NAME from COLUMNS;
+--------------------+----------------------------------------------------+--------------------------------------------+--------------------+
| TABLE_SCHEMA | TABLE_NAME | COLUMN_NAME | COLLATION_NAME |
+--------------------+----------------------------------------------------+--------------------------------------------+--------------------+
转换字符集语句
use information_schema;
SELECT concat("ALTER DATABASE `",table_schema,"` CHARACTER SET = utf8mb4 COLLATE = utf8mb4_unicode_ci;") as _sql
FROM `TABLES` where table_schema like "DB_NAME" group by table_schema;
SELECT concat("ALTER TABLE `",table_schema,"`.`",table_name,"` CONVERT TO CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci;") as _sql
FROM `TABLES` where table_schema like "DB_NAME" group by table_schema, table_name;
SELECT concat("ALTER TABLE `",table_schema,"`.`",table_name, "` CHANGE `",column_name,"` `",column_name,"` ",data_type,"(",character_maximum_length,") CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci;") as _sql
FROM `COLUMNS` where table_schema like "DB_NAME" and data_type in ('varchar');
SELECT concat("ALTER TABLE `",table_schema,"`.`",table_name, "` CHANGE `",column_name,"` `",column_name,"` ",data_type," CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci;") as _sql
FROM `COLUMNS` where table_schema like "DB_NAME" and data_type in ('text','tinytext','mediumtext','long