数据库表结构常用操作

创建表:create table tablename(  id int not null ,  name varchar(20),  primary key(id,name));创建索引:create index indexname on tablename(columnname1,columnname2);删除索引:drop index indexname;删除表:drop table tablename;修改表结构:alter table tablename add(   name1 varchar(20), default("1"),   name2 varchar(20), not null)alter table tablename drop column columnnamealter table tablename modify name1 varchar(30);重命名一列:alter table tablename rename column columnname1 to columnname2放弃主键:alter table FAVOURITEINFO05 drop primary key;