Oracle的增删改查

SQL语句的分类
  数据检索语句：select
  数据操作语句(DML)：insert、delete、update
  数据定义语句(DDL)：alter、drop、truncate、rename、create
  事务控制语句：commit、savepoint、rollback
  数据控制语句(DCL):grant、revoke
  
查数据->select
  语法：select [distinct] {column_name|*...} from table_name;
  eg.select sysdate from dual;   (查询系统时间)
  起别名：select sysdate time from dual;   (time为别名)
          或   select sysdate as time from dual;
          或   select sysdate "date" from dual;   (date为特殊标识符用引号引起来)
  拼接操作:  select sysdate||sysdate from dual;
删数据 ->delete
  语法：delete from table_name [where options];   (只删除数据不删除存储空间)
增数据->insert
  语法:insert into table_name(column_name1,column_name2,..) values(val1,val2,..);
改数据->update
  语法:update teble_name set column_name=value [where condition];