oracle使用序列笔记

create sequence SEQ_SYS_HEYJDEMO_FOLDER_ID  MINVALUE 1 MAXVALUE 999999999999999999999999999  increment by 1 nocache;

create sequence SEQ_SYS_HEYJDEMO_FILE_ID  MINVALUE 1 MAXVALUE 999999999999999999999999999  increment by 1 nocache;

 

drop sequence SEQ_SYS_HEYJDEMO_FOLDER_ID ;

drop sequence SEQ_SYS_HEYJDEMO_FILE_ID ;

-- heyjdemo 文件夹表

create table heyjdemo_folders(

ID number(19,0) not null primary key, -- 文件夹标识

parentID number(19,0) not null,

foldername varchar2(255) not null, -- 文件夹名称

folderinfo varchar2(2000), -- 文件夹描述

fileiconurl varchar2(500) -- 文件夹图标路径

);

 

-- heyjdemo  文件表

create table heyjdemo_files(

ID number(19,0) not null primary key, -- 文件标识

folderID number(19,0) not null constraint heyjdemo_files_ID_FK references heyjdemo_folders(ID) on delete cascade, -- 文件夹标识

filename varchar2(500) not null, -- 文件名

filetype char(10), -- 文件类型

filesize number(19,2), -- 文件大小

fileinfo varchar2(2000), -- 文件描述

fileurl varchar2(500) not null, -- 文件路径

fileiconurl varchar2(500) -- 文件图标

);

 

 

 

-- 向heyjdemo_folders插入记录

insert into heyjdemo_folders (ID, parentID, foldername, folderinfo)  values(SEQ_SYS_HEYJDEMO_FOLDER_ID.Nextval,'0','计算机科学','计算机科学');

insert into heyjdemo_folders (ID, parentID, foldername, folderinfo)  values(SEQ_SYS_HEYJDEMO_FOLDER_ID.Nextval,'0','文学','文学');

insert into heyjdemo_folders (ID, parentID, foldername, folderinfo)  values(SEQ_SYS_HEYJDEMO_FOLDER_ID.Nextval,'1','数据结构','数据结构');

insert into heyjdemo_folders (ID, parentID, foldername, folderinfo)  values(SEQ_SYS_HEYJDEMO_FOLDER_ID.Nextval,'1','C语言','C语言');

insert into heyjdemo_folders (ID, parentID, foldername, folderinfo)  values(SEQ_SYS_HEYJDEMO_FOLDER_ID.Nextval,'0','c#','c#');

insert into heyjdemo_folders (ID, parentID, foldername, folderinfo)  values(SEQ_SYS_HEYJDEMO_FOLDER_ID.Nextval,'0','oracle','oracle');

insert into heyjdemo_folders (ID, parentID, foldername, folderinfo)  values(SEQ_SYS_HEYJDEMO_FOLDER_ID.Nextval,'5','数据库','数据库');

insert into heyjdemo_folders (ID, parentID, foldername, folderinfo)  values(SEQ_SYS_HEYJDEMO_FOLDER_ID.Nextval,'5','mysql','mysql');

insert into heyjdemo_folders (ID, parentID, foldername, folderinfo)  values(SEQ_SYS_HEYJDEMO_FOLDER_ID.Nextval,'5','java','java');

insert into heyjdemo_folders (ID, parentID, foldername, folderinfo)  values(SEQ_SYS_HEYJDEMO_FOLDER_ID.Nextval,'0','jsp','jsp');

insert into heyjdemo_folders (ID, parentID, foldername, folderinfo)  values(SEQ_SYS_HEYJDEMO_FOLDER_ID.Nextval,'0','我的文档','我的文档');

 

-- 向heyjdemo_files中插入记录

insert into heyjdemo_files (ID, folderID, filename, fileurl) values(SEQ_SYS_HEYJDEMO_FILE_ID.Nextval, 1, '计算机教程' ,'/' );

insert into heyjdemo_files (ID, folderID, filename, fileurl) values(SEQ_SYS_HEYJDEMO_FILE_ID.Nextval, 4, 'c语言教程' ,'/');

insert into heyjdemo_files (ID, folderID, filename, fileurl) values(SEQ_SYS_HEYJDEMO_FILE_ID.Nextval, 3, '数据结构教程' ,'/');

insert into heyjdemo_files (ID, folderID, filename, fileurl) values(SEQ_SYS_HEYJDEMO_FILE_ID.Nextval, 1, 'tt' ,'/');

insert into heyjdemo_files (ID, folderID, filename, fileurl) values(SEQ_SYS_HEYJDEMO_FILE_ID.Nextval, 5, 'ttt' ,'/');

insert into heyjdemo_files (ID, folderID, filename, fileurl) values(SEQ_SYS_HEYJDEMO_FILE_ID.Nextval, 8, 'tttt' ,'/');

怎么修改序列？？

创建序列有什么要求嘛，或者说有什么规则吗

我也只知道这么用，但不明白为什么要这么用，在做插入操作时，要看看序列的最大值，如果id小于序列的值，就会报错。