oracle树形查询 start with connect by

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mb5fe9476706301 2019-10-11 10:35:00

一、简介

　　在oracle中start with connect by (prior) 用来对树形结构的数据进行查询。其中start with conditon 给出的是数据搜索范围, connect by后面给出了递归查询的条件,prior 关键字表示父数据，prior 条件表示子数据需要满足父数据的什么条件。如下

start with id= '10001' connect by prior parent_id= id and prior num = 5

表示查询id为10001，并且递归查询parent_id=id,为5的记录。

二、实例

　　1、构造数据

1 -- 表结构
 2 create table menu(
 3  id varchar2(64) not null,
 4  parent_id varchar2(64) not null,
 5  name varchar2(100) not null,
 6  depth number(2) not null,
 7  primary key (id)
 8 )
 9 
10 -- 初始化数据
11 -- 顶级菜单
12 insert into menu values ('100000', '0', '顶级菜单1', 1);
13 insert into menu values ('200000', '0', '顶级菜单2', 1);
14 insert into menu values ('300000', '0', '顶级菜单3', 1); 
15 
16 -- 父级菜单
17 -- 顶级菜单1 直接子菜单
18 insert into menu values ('110000', '100000', '菜单11', 2);
19 insert into menu values ('120000', '100000', '菜单12', 2);
20 insert into menu values ('130000', '100000', '菜单13', 2);
21 insert into menu values ('140000', '100000', '菜单14', 2); 
22 -- 顶级菜单2 直接子菜单
23 insert into menu values ('210000', '200000', '菜单21', 2);
24 insert into menu values ('220000', '200000', '菜单22', 2);
25 insert into menu values ('230000', '200000', '菜单23', 2); 
26 -- 顶级菜单3 直接子菜单
27 insert into menu values ('310000', '300000', '菜单31', 2); 
28 
29 -- 菜单13 直接子菜单
30 insert into menu values ('131000', '130000', '菜单131', 3);
31 insert into menu values ('132000', '130000', '菜单132', 3);
32 insert into menu values ('133000', '130000', '菜单133', 3);
33 
34 -- 菜单132 直接子菜单
35 insert into menu values ('132100', '132000', '菜单1321', 4);
36 insert into menu values ('132200', '132000', '菜单1332', 4);
37

　　生成的菜单层次结构如下：

顶级菜单1

菜单11

菜单12

菜单13

菜单131

菜单132

菜单1321

菜单1322

菜单133

菜单14

顶级菜单2

菜单21

菜单22

菜单23

顶级菜单3

菜单31

　　2、SQL查询

--prior放的左右位置决定了检索是自底向上还是自顶向下. 左边是自上而下（找子节点），右边是自下而上（找父节点）
--找父节点
select * from menu start with id='130000' connect by id = prior parent_id;

　　 oracle树形查询 start with connect by_父节点

--找子节点节点
-- (子节点)id为130000的菜单，以及130000菜单下的所有直接或间接子菜单(prior 在左边， prior、parent_id(等号右边)在右边）
select * from menu start with id='130000' connect by prior id =  parent_id  ;

　　 oracle树形查询 start with connect by_子菜单_02

-- (父节点)id为1321的菜单，以及1321菜单下的所有直接或间接父菜单(prior、parent_id(等号左边) 都在左边)
select * from menu start with id='132100' connect by prior parent_id = id;
-- prior 后面跟的是(parent_id) 则是查找父节点,prior后面跟的是(id)则是查找子节点

　　 oracle树形查询 start with connect by_父节点_03

--根据菜单组分类统计每个菜单包含子菜单的个数
select id, max(name) name, count(1) from menu 
group by id
connect by prior parent_id = id
order by id

　　 oracle树形查询 start with connect by_子节点_04

-- 查询所有的叶子节点
select t2.* from menu t2 where id not in(select t.parent_id from menu t) order by id;

　　 oracle树形查询 start with connect by_子菜单_05

三、性能问题　　

　　对于 start with connect by语句的执行，oracle会进行递归查询，当数据量大的时候会产生性能相关问题。

--生成执行计划
explain plan for select * from menu start with id='132100' connect by prior parent_id = id;

-- 查询执行计划
select *  from  table( dbms_xplan.display);

　　语句执行计划结果如下：

Plan hash value: 3563250490

----------------------------------------------------------------------------------------------
| Id  | Operation                     | Name         | Rows  | Bytes | Cost (%CPU)| Time     |
----------------------------------------------------------------------------------------------
|   0 | SELECT STATEMENT              |              |     1 |   133 |     1   (0)| 00:00:01 |
|*  1 |  CONNECT BY WITH FILTERING    |              |       |       |            |          |
|   2 |   TABLE ACCESS BY INDEX ROWID | MENU         |     1 |   133 |     1   (0)| 00:00:01 |
|*  3 |    INDEX UNIQUE SCAN          | SYS_C0018586 |     1 |       |     1   (0)| 00:00:01 |
|   4 |   NESTED LOOPS                |              |       |       |            |          |
|   5 |    CONNECT BY PUMP            |              |       |       |            |          |
|   6 |    TABLE ACCESS BY INDEX ROWID| MENU         |     1 |   133 |     1   (0)| 00:00:01 |
|*  7 |     INDEX UNIQUE SCAN         | SYS_C0018586 |     1 |       |     1   (0)| 00:00:01 |
----------------------------------------------------------------------------------------------

Predicate Information (identified by operation id):
---------------------------------------------------

   1 - access("ID"=PRIOR "PARENT_ID")
   3 - access("ID"='132100')
   7 - access("ID"=PRIOR "PARENT_ID")

Note
-----
   - dynamic sampling used for this statement