修改已建表的默认编码:ALTER TABLE A DEFAULT CHARACTER SET gbk;
查看表的结构:desc tablename;
查看表的建表结构:show create table tablename;
查看数据库编码格式:show variables like 'character_set_database';
修改数据库的编码格式:alter database databaseName character set utf8;
修改表的字段编码:ALTER TABLE `tableName` CHANGE `columnName` `columnName` varchar(20) CHARACTER SET utf8 COLLATE utf8_bin not null;
删除外键: alter table employee drop foreign key FK_EMPLOYEE_REFERENCE_DEPARTME;
删除表: drop table employee;
设置表的自增长:alter table tableName modify columnName int auto_increment;
设置默认值:ALTER TABLE 表名 ALTER 字段名 SET DEFAULT 默认值;
删除默认值:ALTER TABLE 表名 ALTER 字段名 DROP DEFAULT;
修改表字段长度:alter table signlog modify column late varchar(10);
添加不为null字段:alter table employee add password varchar(20) default '123';