环境:8icreate table dali.dep(depid int,depname varchar2(10));
create table dali.emp(depid int,name varchar2(10));
insert into dali.dep values(100,'人力资源部');
insert into dali.dep values(101,'人事科');
insert into dali.dep values(102,'档案室');
insert into dali.dep values(200,'软件开发部');
insert into dali.dep values(201,'技术支持班');
insert into dali.dep values(202,'开发组');
insert into dali.emp values(201,'唐五');
insert into dali.emp values(201,'窦六');
insert into dali.emp values(102,'李四');
insert into dali.emp values(202,'黄七');
insert into dali.emp values(101,'王二');
insert into dali.emp values(101,'张三');
create table dali.emp(depid int,name varchar2(10));
insert into dali.dep values(100,'人力资源部');
insert into dali.dep values(101,'人事科');
insert into dali.dep values(102,'档案室');
insert into dali.dep values(200,'软件开发部');
insert into dali.dep values(201,'技术支持班');
insert into dali.dep values(202,'开发组');
insert into dali.emp values(201,'唐五');
insert into dali.emp values(201,'窦六');
insert into dali.emp values(102,'李四');
insert into dali.emp values(202,'黄七');
insert into dali.emp values(101,'王二');
insert into dali.emp values(101,'张三');
设计不合理,很麻烦。改变结构用BOM算法,很容易实现=====================================
请问如何改变结构,可以谈谈BOM算法吗?
create table tree(a int,b int);
insert into tree values (1,null);
insert into tree values (2,1);
insert into tree values (3,1);
insert into tree values (4,2);--特点存储冗余,查询速度快
create table tree(a varchar2(50));
insert into tree values('01');
insert into tree values('01001');
insert into tree values('01002');
insert into tree values('01001001');
例如:
一级id:100,200,300
二级id:100100,100200,100300,
三级id:100100100,100200100,100300100
这样你就可以很容易的产生三层查询。