dllxy2的专栏

 Oracle 9i共提供了16种标量数据类型，如表7.4所示。Oracle 9i的标量数据类型名称                                                    含义 Char      用于描述定长的字符型数据，长度varchar2    用于描述变长的字符型数据，长度nchar    用来存储Unicode字符集的定长字符型数据，长度nvarchar2

oracle中ROWNUM表示行号，比如你想返回前10行,sql如下:select * from mytable where ROWNUM如果返回90-100行，那行下面的语句是不对的:select * from mytable where ROWNUM>90 and ROWNUMoracle用下面语句方法一select * from mytable where ROWNUM>

1。先创建一个序列：create  sequence mytable_sequencestart with 1increment by 12.给表创建触发器:create or replace trigger mytable_trgbefore insert on mytablefor each rowbeginselect mytable_sequence.nextval into ne