oracle alter语句用法
sql>
sql> create table bar ( n number );
table created.
sql>
sql> alter table bar add c char(1);
table altered.
sql>
sql> drop table bar;
table dropped.
sql>
增加一个日期字段
sql>
sql> create table bar ( n number );
table created.
sql>
sql>  alter table bar add d date;
table altered.
sql>
sql>  object_type, status
  2      from user_objects
  3     where object_name = 'shield'
  4    /
object_type         status
------------------- -------
package             valid
package body        valid
sql>
sql> drop table bar;
table dropped.
sql>
给己有表的增加字段
sql> -- create demo table
sql> create table employee(
  2    id                 varchar2(4 byte)         not null,
  3    first_name         varchar2(10 byte),
  4    last_name          varchar2(10 byte),
  5    start_date         date,
  6    end_date           date,
  7    salary             number(8,2),
  8    city               varchar2(10 byte),
  9    description        varchar2(15 byte)
 10  )
 11  /
table created.