identifiy 是定义自动增加的列,就像是自动编号,以前在做.net开发中使用sqlserver的时候也有这类的方法。这个值的特点就是不会重复,所以叫它自动生成的唯一值。以下是生成的两种方式:GENERATED BY ALWAYS AS IDENTITY GENERATED BY DEFAULT AS IDENTITYBy always和by default是说明生成这个identifiy的方式B...【阅读全文】
3、Which structure can span multiple data files?A) a permanent tablespaceB) a bigfile tablespaceC) a temporary tablespaceD) a segmentE) an extentAnswer:ACD【阅读全文】
2、Which two are true about Optimizer Statistics?? A) They do not persist across Instance restarts.? B) They are automatically updated when DDL statements execute.? C) They are gathered by the Manageability Monitor (MMON) background process.? D) They can be gathered by executing th...【阅读全文】
博客文章除注明转载外,均为原创。转载请注明出处。本文链接地址:http://blog.chinaunix.net/uid-31396856-id-5784934.htmlOracle视图except SNAP_ID, and INSTANCE_NUMBER等字段dba_hist_active_sess_history视图的详细信息,请见下表列数据类型NULL...【阅读全文】
一、同义词同义词=表的别名,为不同用户间的数据访问带来方便的机制。创建同义词的语法:(需要管理员权限操作)create[public]synonym同义词名称for数据库对象;范例:create synonym myemp for c##scott.emp;select * from myemp;此时myemp只能被sys用户使用,要想让所有用户使用,就要创建公共同义词。drop synon...【阅读全文】