Oracle 中的递归语句Select...Start With...Connect by prior...的使用

在做项目中，我们经常会遇到树形数据，在oracle树查询的最重要的就是select…start with…connect by…prior语法了。根据该语法，我们可以将一个表形结构的以树的顺序列出来。

 

SQL脚本用来创建表、序列、索引、测试数据等、

drop table t_dept;
drop sequence seq_dept;
drop index t_index_parent_id;
drop index t_index_dept_code;

 

--创建表;
create table t_dept (
       deptid number not null primary key,
       dentname_en varchar2(200) not null,
       deptname_cn varchar2(200) not null,
       deptcode varchar2(200) not null,
       parent_id number(10)  default -1);

 

      
--创建序列;
create sequence seq_dept 
start with 100
increment by 1
minvalue 1
maxvalue 1000000
nocycle 
cache 20;  

 

--创建索引;
create index t_index_parent_id on scott.t_dept(parent_id);
create index t_index_dept_code on t_dept(deptcode);

 

--插入测试数据;
insert into scott.t_dept values(seq_dept.nextval,'Front Office Department','前台部','0'||seq_dept.nextval,-1); 
insert into scott.t_dept values(seq_dept.nextval,'Financial Department','财务部','0'||seq_dept.nextval,-1); 
insert into scott.t_dept values(seq_dept.nextval,'Logistics Department','后勤部','0'||seq_dept.nextval,-1); 
insert into scott.t_dept values(seq_dept.nextval,'Recruiting Department','招聘部','0'||seq_dept.nextval,-1); 
insert into scott.t_dept values(seq_dept.nextval,'Development department','开发部','0'||seq_dept.nextval,-1); 
insert into scott.t_dept values(seq_dept.nextval,'Dngineering department','工程部','0'||seq_dept.nextval,-1); 
insert into scott.t_dept values(seq_dept.nextval,'Front Office Department_001','前台接待分部','0'||seq_dept.nextval,100); 
insert into scott.t_dept values(seq_dept.nextval,'Front Office Department_002','前台分流部','0'||seq_dept.nextval,100); 
insert into scott.t_dept values(seq_dept.nextval,'Front Office Department_003','前台引导客流部','0'||seq_dept.nextval,100); 
insert into scott.t_dept values(seq_dept.nextval,'Receptionist Department_001','前台接待普通客户部','0'||seq_dept.nextval,106); 
insert into scott.t_dept values(seq_dept.nextval,'Receptionist Department_002','前台接待中级客户部','0'||seq_dept.nextval,106); 
insert into scott.t_dept values(seq_dept.nextval,'Receptionist Department_003','前台接待高级客户部','0'||seq_dept.nextval,106); 
insert into scott.t_dept values(seq_dept.nextval,'Sweep the toilet Department','扫厕所分部','0'||seq_dept.nextval,102); 
insert into scott.t_dept values(seq_dept.nextval,'Logistical support Department','后勤保障部','0'||seq_dept.nextval,102); 
insert into scott.t_dept values(seq_dept.nextval,'Clean the health','打扫卫生分部','0'||seq_dept.nextval,102); 
insert into scott.t_dept values(seq_dept.nextval,'Men lavatory men toilet','打扫男厕所分部','0'||seq_dept.nextval,112); 
insert into scott.t_dept values(seq_dept.nextval,'Women lavatory','打扫女厕所分部','0'||seq_dept.nextval,112); 
insert into scott.t_dept values(seq_dept.nextval,'PHP Development department','PHP开发部','0'||seq_dept.nextval,104); 
insert into scott.t_dept values(seq_dept.nextval,'.Net Development department','.NET开发部','0'||seq_dept.nextval,104); 
insert into scott.t_dept values(seq_dept.nextval,'Java Development department','Java开发部','0'||seq_dept.nextval,104); 
insert into scott.t_dept values(seq_dept.nextval,'C++ Development department','C++开发部','0'||seq_dept.nextval,104); 
insert into scott.t_dept values(seq_dept.nextval,'Python Development department','Python开发部','0'||seq_dept.nextval,104); 
insert into scott.t_dept values(seq_dept.nextval,'Java Development department_001','Java前台开发部','0'||seq_dept.nextval,123); 
insert into scott.t_dept values(seq_dept.nextval,'Java Development department_002','Java后台开发部','0'||seq_dept.nextval,123); 
commit;

 

--所有t_dept表中的数据结果为：

 

 

--根据子部门查询出父部门(当prior parent = id时，数据库会跟据当前的parent来迭代出与当前的parent相同的id的记录，所以查询出来的结果就是所有的父类结果)。
select deptid, dentname_en, deptname_cn, deptcode, parent_id, level
  from scott.t_dept
 start with deptid = 109
connect by prior parent_id = deptid;

等效于:

--根据子部门查询出父部门
select deptid, dentname_en, deptname_cn, deptcode, parent_id, level
  from scott.t_dept
  start with deptid = 109
  connect by deptid = prior parent_id;

 查询结果：

 

 

 

--根据父部门查询出子部门(当parent = prior id时，数据库会根据当前的id迭代出parent与该id相同的记录，所以查询的结果是迭代出了所有的子类记录)；
select deptid, dentname_en, deptname_cn, deptcode, parent_id, level
  from scott.t_dept
 start with deptid = 100
connect by parent_id = prior deptid ;

等效于:

--根据父部门查询出子部门
select deptid,dentname_en,deptname_cn,deptcode,parent_id,level
  from scott.t_dept dept
 start with deptid = 100
connect by prior dept.deptid = dept.parent_id;

 查询结果：

 

--根据当前子部门查询出顶级部门ID以及部门Name：(oracle11g里面可以采用connect_by_root，非常的方便)
select *
  from t_dept d
 where d.deptid = (select distinct FIRST_VALUE(deptid) OVER(ORDER BY LEVEL DESC ROWS UNBOUNDED PRECEDING) AS firstdeptid
                     from t_dept
                    start with deptid = 109
                   connect by prior parent_id = deptid);

查询 结果：