Oracle connect by prior 处理树状表

Posted 2023-04-24 丹心石

--基础篇
--1.建表
create table department(departmentid integer,departmentname varchar2(30),upperdepartmentid integer,manager varchar2(30));
--2.建序列
create sequence department_seq  start with 1 nocycle;
--3.建触发器
create trigger tr_department_id before insert on department
for each row 
begin
  select department_seq.nextval into :new.departmentid from dual;
end;
--4.建存储过程
create or replace procedure pr_add_department(deptName in varchar2,upperDeptName in varchar2) as
  pid integer;
begin
  if nvl(upperDeptName,\'0\')=\'0\' then
     pid:=0;
  else
    select departmentid into pid from department where departmentname=upperDeptName;
  end if;
  insert into department(departmentname,upperdepartmentid) values(deptName,pid);
  commit;
end;

--5.查询
select * from department;
--6.更新
update department set departmentname=\'会计电算化\',upperdepartmentid=9 where departmentid=10;

--7.添加树状表树根
begin
  pr_add_department(\'江西财经学院\',\'\');
end;
--8.添加分支
begin
  --pr_add_department(\'信息系\',\'江西财经学院\');
  pr_add_department(\'会计专业\',\'江西财经学院\');
end;
--9.查询树状表  level 分层级
select departmentid,departmentname,upperdepartmentid,level
 from department
connect by prior departmentid=upperdepartmentid
start with upperdepartmentid=0

oracle中connect by prior的使用

作用

connect by主要用于父子，祖孙，上下级等层级关系的查询

语法

{ CONNECT BY [ NOCYCLE ] condition [AND condition]... [ START WITH condition ]
| START WITH condition CONNECT BY [ NOCYCLE ] condition [AND condition]...}

解释：

start with: 指定起始节点的条件

connect by: 指定父子行的条件关系

prior: 查询父行的限定符，格式: prior column1 = column2 or column1 = prior column2 and ... ，

nocycle: 若数据表中存在循环行，那么不添加此关键字会报错，添加关键字后，便不会报错，但循环的两行只会显示其中的第一条

循环行: 该行只有一个子行，而且子行又是该行的祖先行

connect_by_iscycle: 前置条件:在使用了nocycle之后才能使用此关键字，用于表示是否是循环行，0表示否，1 表示是

connect_by_isleaf: 是否是叶子节点，0表示否，1 表示是

level: level伪列,表示层级，值越小层级越高，level=1为层级最高节点

例子

自定义数据

-- 创建表
create table employee(
       emp_id number(18),
       lead_id number(18),
       emp_name varchar2(200),
       salary number(10,2),
       dept_no varchar2(8)
);

-- 添加数据
insert into employee values(‘1‘,0,‘king‘,‘1000000.00‘,‘001‘);
insert into employee values(‘2‘,1,‘jack‘,‘50500.00‘,‘002‘);
insert into employee values(‘3‘,1,‘arise‘,‘60000.00‘,‘003‘);
insert into employee values(‘4‘,2,‘scott‘,‘30000.00‘,‘002‘);
insert into employee values(‘5‘,2,‘tiger‘,‘25000.00‘,‘002‘);
insert into employee values(‘6‘,3,‘wudde‘,‘23000.00‘,‘003‘);
insert into employee values(‘7‘,3,‘joker‘,‘21000.00‘,‘003‘);commit;

查询以emp_id为0开始的节点的所有直属节点

select emp_id,lead_id,emp_name,prior emp_name as lead_name,salary
     from employee
     start with  lead_id=0
     connect by prior emp_id =  lead_id 

　　-- 等同于

　　　select emp_id,lead_id,emp_name,prior emp_name as lead_name,salary
     from employee
     start with  emp_id=1
     connect by prior emp_id =  lead_id

查询以emp_id为6开始的节点

       select emp_id,lead_id,emp_name,salary
       from employee 
       start with emp_id=6
       connect by prior lead_id=emp_id;

level伪列的使用，格式化层级

select lpad(‘ ‘,level*2,‘ ‘)||emp_name as name,emp_id,lead_id,salary,level
       from employee
       start with lead_id=0
       connect by prior emp_id=lead_id

connect_by_root 查找根节点

select connect_by_root emp_name,emp_name,lead_id,salary
       from employee  
       where dept_no=‘002‘
       start with lead_id=1
       connect by  prior emp_id = lead_id;

标注循环行

-- 插入一条数据，与另一条emp_id=7的数据组成循环行
       insert into employee values(‘3‘,7,‘joker_cycle‘,‘21000.00‘,‘003‘);
       commit;
       -- connect_by_iscycle("CYCLE"), connect by nocycle
       select emp_id,emp_name,lead_id,salary,connect_by_iscycle as cycle 
       from employee 
       start with lead_id=0
       connect by nocycle prior emp_id = lead_id;

connect_by_isleaf 是否是叶子节点

select emp_id,emp_name,lead_id,salary,connect_by_isleaf
       from employee
       start with lead_id=0
       connect by nocycle prior emp_id=lead_id;