mysql(5.7.17)字符集设置(character_set/collation)

0 查看字符集(character_set/collation)

use information_schema;desc tables;    --一定记住tables表，information_schema中的metadata都可以查到-- 查看db的默认，DEFAULT_CHARACTER_SET_NAME/DEFAULT_COLLATION_NAMEselect * from schemata where schema_name = 'db_name';-- 查看table的，只有table_collation字段select * from tables where table_schema = 'db_name' and table_name = 'table_name';-- 查看column的，CHARACTER_SET_NAME/COLLATION_NAME都要select * from columns where table_schema = 'db_name' and table_name = 'table_name';

--查看mysql支持的character_set，Default collation是默认的"大小写敏感"select * from information_schema.character_sets;    --就是执行了上面的sqlshow charset;

/*查看各character set的collation，以gbk为例gbk_chinese_ci是"大小写不敏感"，ci是case sensitive的缩写gbk_bin是"大小写敏感"，以二进制(binary)存储*/select * from information_schema.collations;show collation;

show variables like 'character_set%';   --查看当前环境的character_set

show variables like 'collation%';   --查看当前的collation

1 my.ini配置character_set

-- 注意位置，放在[client]和[mysql]都可以，效果相同，以后面的为准。放在[mysqld]下服务不能启动。default-character-set = utf8-- 上句设置之后，对应的全局变量改变character_set_client = utf8character_set_connection = utf8 character_set_results = utf8-- 注意位置，放在[mysqld]下character-set-server = gbkcollation-server = gbk_bin-- 上句设置之后，对应的全局变量改变character_set_database = gbk character_set_server = gbk    --默认的create database db时的character_set，其他的含义待测试，可根据字面单词猜想collation_database = gbk_bincollation_server = gbk_bin

2 数据库的character_set指定/修改

-- 默认db的character_set和@@character_set_server一致，table和db一致，column和table一致create database db;-- defalut可有可无，注意gbk的default collation(上面有)是gbk_chinese_ci(大小写不敏感)-- 即使collation_database/server都是gbk_bin，创建的db默认仍是gbk_chinese_ci，这里专门指定create datadbase db character set gbk collate gbk_bin;create datadbase db default character set gbk collate gbk_bin;  --正确alter datadbase db character set gbk collate gbk_bin;       --正确alter datadbase db convert to character set gbk collate gbk_bin;    --错误，不支持convert to

3 table的character_set指定/修改

create table t1(c1 varchar2) character set gbk collate gbk_chinese_ci;-- 测试insert into t1 values('a');select * from t1 where c1 = 'A';    --返回'a'，此时'a'='A'--注意以下两种方法的差别，第1句是只是修改默认alter table t1 character set gbk collate gbk_bin;   --提示Records: 0--测试alter table t1 add c2 varchar(50);insert into t1 values('b','b');select * from t1 where c1 = 'A';    --返回'a'，c1仍然是gbk_chinese_ciselect * from t1 where c2 = 'B';    --返回empty，c2是gbk_bin--已有字段c1,c2及再添加的默认都是gbk_binalter table t1 convert to character set gbk collate gbk_bin;    --提示Records: 1

4 column的character_set指定/修改

-- 套路相同alter table add c1 varchar(50) character set gbk collate gbk_bin;alter table t1 change c1 c1 varchar(50) character set gbk collate gbk_bin;