connect by prior
2024-04-10 23:20:12
1. connect by prior 介绍
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为层级最高节点个人理解：
connect by prior 是oracle 提供的一个查询表数据的树形结构的功能。
connect by prior 用法模式介绍：
connect by prior id = father_id start with id = x;
通过start with id=x 或者 start with father_id=x 获取第一行数据；
然后再通过connect by prior id = father_id 获取第二行及以后的数据，这里prior 表示之前
的意思，prior id = father_id 表示要取的father_id 的值来自上次取的id的值。
connect by prior id = father_id start with id = x0 可以这样递推：
根据id=x0 获取 对应的行1，
根据father_id = x0 获取对应的行2， 获取对应的id=x2;
根据father_id=x2 获取对应的行3，获取对应的id=x3;
…
示例：
create table t1(id int, father_id int);
insert into t1 values(1,0);
insert into t1 values(2,1);
insert into t1 values(12,1);
insert into t1 values(3,2);
insert into t1 values(102,101);SQL> select id, father_id, level from t1 connect by prior id = father_id start with id=1;ID FATHER_ID LEVEL
---------- ---------- ----------1 0 12 1 23 2 312 1 2SQL> select id, father_id, level from t1 connect by id = prior father_id start with id=2;ID FATHER_ID LEVEL
---------- ---------- ----------2 1 11 0 2增加一行，使出现循环
SQL> insert into t1 values(1,1);1 row created.SQL> select id, father_id, level from t1 connect by prior id = father_id start with id=1;
ERROR:
ORA-01436: CONNECT BY loop in user dataSQL> select id, father_id, level from t1 connect by nocycle prior id = father_id start with id=1;ID FATHER_ID LEVEL
---------- ---------- ----------1 0 12 1 23 2 312 1 21 1 12 1 23 2 312 1 2
：：如果循环id=father_id 出现开头，如上，会出现2份。如果是中间出现的则忽略该行SQL> select * from t1 order by 1,2; ID FATHER_ID
---------- ----------1 02 12 23 24 312 1102 1017 rows selected.SQL> select id, father_id, level from t1 connect by nocycle prior id = father_id start with id=1;ID FATHER_ID LEVEL
---------- ---------- ----------1 0 12 1 23 2 34 3 412 1 22. 功能实现
初步实现connect by prior id=father_id start with id=x
#include <iostream>
#include <list>
using namespace std;typedef struct
{int id;int father_id;
}id_pid;/** show list node*/
void show_nodes(list<id_pid>&list_data)
{list<id_pid>::iterator it;cout<<"list node:"<<endl;for(it=list_data.begin(); it!=list_data.end(); it++){cout<<it->id<<'\t'<<it->father_id<<endl;}
}/** add node*/
void add_nodes(list<id_pid> &list_data)
{int i = 0;int total = 3;id_pid data_value;while(i++ < total){data_value.father_id = i;data_value.id = i+1;list_data.push_back(data_value);}
#if 1while(i++ < total+10){data_value.father_id = i;data_value.id=i+i%2;list_data.push_back(data_value);}
#endif
}/** get the first node*/
bool get_first_value(list<id_pid> &list_task1, list<id_pid>&list_data, int father_id)
{list<id_pid>::iterator it;for(it=list_data.begin(); it!=list_data.end(); it++){if(father_id == it->father_id){id_pid data_value;data_value.id = it->id;data_value.father_id = it->father_id;list_task1.push_back(data_value);it=list_data.erase(it);}}return list_data.size() == 0 ? false:true;
}/** connect by prior*/
void get_connect_by_prior(list<id_pid>&list_task1, list<id_pid> &list_data ,list<id_pid> &list_res)
{list<id_pid>::iterator it;int father_id;id_pid data_value;list<id_pid> list_task2;while(list_task1.size()>0){for(it=list_task1.begin(); it!=list_task1.end(); it++){data_value.id = it->id;data_value.father_id = it->father_id;list_res.push_back(data_value);father_id = it->id;get_first_value(list_task2, list_data, father_id);}list_task1 = list_task2;list_task2.clear();}}int main()
{list<id_pid> list_data;list<id_pid> list_task1;list<id_pid> list_res;add_nodes(list_data);show_nodes(list_data);get_first_value(list_task1, list_data, 1);get_connect_by_prior(list_task1, list_data, list_res);show_nodes(list_res);}测试结果：
[wl@host122 cpp]$ ./connect1
list node:
2 1
3 2
4 3
6 5
6 6
8 7
8 8
10 9
10 10
12 11
12 12
14 13
result:
2 1
3 2
4 3
3. 语法改写 connect by prior
create table x1(id int, father_id int, name char(10), id4 int);
insert into x1 values(101, 100, 'n1', 1);
insert into x1 values(102, 101, 'n2', 2);
insert into x1 values(112, 101, 'n3', 3);
insert into x1 values(103, 102, 'n4', 4);
insert into x1 values(113, 112, 'n5', 5);
insert into x1 values(114, 113, 'n6', 6);
insert into x1 values(201, 200, 'n7', 7);3.1 语法改写 connect by prior id = father_id start with father_id = 100
测试语句
select id, father_id, level from x1 connect by prior id = father_id
start with father_id = 100;
改写为mysql 支持的语句如下：
select id, father_id, level, pathlevel from
(select id, father_id,@le:= if (father_id = 100 , 1, if( locate( concat('|',father_id,':'), @pathlevel) > 0,substring_index( substring_index(@pathlevel,concat('|',father_id,':'),-1),'|',1) +1, -1) ) level,@pathlevel:= concat(@pathlevel,'|',id,':', @le ,'|') pathlevelfrom (select id, father_id from db2.x1 order by 1,2)temp1,(select @le := 1,@pathlevel := '')temp2
)xxx
where level > 0;执行测试
oracle 执行结果
SQL> select id, father_id, level from x1 connect by prior id = father_id 2 start with father_id = 100; ID FATHER_ID LEVEL
---------- ---------- ----------101 100 1102 101 2103 102 3112 101 2113 112 3114 113 46 rows selected.mysql 执行结果
+------+-----------+-------+--------------------------------------------+
| id | father_id | level | pathlevel |
+------+-----------+-------+--------------------------------------------+
| 101 | 100 | 1 | |101:1| |
| 102 | 101 | 2 | |101:1||102:2| |
| 103 | 102 | 3 | |101:1||102:2||103:3| |
| 112 | 101 | 2 | |101:1||102:2||103:3||112:2| |
| 113 | 112 | 3 | |101:1||102:2||103:3||112:2||113:3| |
| 114 | 113 | 4 | |101:1||102:2||103:3||112:2||113:3||114:4| |
+------+-----------+-------+--------------------------------------------+
6 rows in set (0.01 sec)3.2 语法改写 connect by prior id = father_id start with id = 101
测试语句
select id, father_id, level from x1 connect by prior id = father_id
start with id = 101;
改写为mysql 支持的语句如下：
select id, father_id, 1 as level, concat('|', id, ':0|') as pathlevel from db2.x1 where id = 101
union
select id, father_id, level, pathlevel from
(select id, father_id,@le:= if (father_id = 101 , 2, if( locate( concat('|',father_id,':'), @pathlevel) > 0,substring_index( substring_index(@pathlevel,concat('|',father_id,':'),-1),'|',1) +1, -1) ) level,@pathlevel:= if(@le = -1, @pathlevel, concat(@pathlevel,'|',id,':', @le ,'|')) pathlevelfrom (select id, father_id from db2.x1 where id != 101 order by 1,2)temp1,(select @le := 2,@pathlevel := '|101:0|')temp2
)xxx
where level > 0;执行测试
oracle 执行结果
SQL> select id, father_id, level from x1 connect by prior id = father_id start with id=101;ID FATHER_ID LEVEL
---------- ---------- ----------101 100 1102 101 2103 102 3112 101 2113 112 3114 113 46 rows selected.mysql 执行结果
+------+-----------+-------+--------------------------------------------+
| id | father_id | level | pathlevel |
+------+-----------+-------+--------------------------------------------+
| 101 | 100 | 1 | |101:0| |
| 102 | 101 | 2 | |101:0||102:2| |
| 103 | 102 | 3 | |101:0||102:2||103:3| |
| 112 | 101 | 2 | |101:0||102:2||103:3||112:2| |
| 113 | 112 | 3 | |101:0||102:2||103:3||112:2||113:3| |
| 114 | 113 | 4 | |101:0||102:2||103:3||112:2||113:3||114:4| |
+------+-----------+-------+--------------------------------------------+
6 rows in set (0.00 sec)
4. sys_connect_by_path
4.1 sys_connect_by_path … start with father_id = x
测试语句
select id, father_id, level, sys_connect_by_path(id, ‘/’) as paths from x1
connect by prior id = father_id
start with father_id = 100;
等价写法：
select id, father_id, level, pathnodes from
(select id, father_id,@le:= if (father_id = 100 , 1, if( locate( concat('|',father_id,':'), @pathlevel) > 0,substring_index( substring_index(@pathlevel,concat('|',father_id,':'),-1),'|',1) +1, -1) ) level,@pathlevel:= if(@le = -1, @pathlevel, concat(@pathlevel,'|',id,':', @le ,'|')) pathlevel,@pathnodes:= if( father_id = 100, concat('/', id), concat_ws('/',if( locate( concat('|',father_id,':'),@pathall) > 0 , substring_index( substring_index(@pathall,concat('|', father_id, ':'),-1),'|',1),@pathnodes ) ,id ) )pathnodes,@pathall:=concat(@pathall,'|',id,':', @pathnodes ,'|') pathall from (select id, father_id from db2.x1 order by 1,2)temp1,(select @le := 1,@pathlevel := '',@pathall:='',@pathnodes:='')temp2
)xxx
where level > 0;测试结果
oracle 执行结果101 100 1 /101102 101 2 /101/102103 102 3 /101/102/103112 101 2 /101/112113 112 3 /101/112/113114 113 4 /101/112/113/1146 rows selected.mysql 执行结果+------+-----------+-------+------------------+
| id | father_id | level | pathnodes |
+------+-----------+-------+------------------+
| 101 | 100 | 1 | /101 |
| 102 | 101 | 2 | /101/102 |
| 103 | 102 | 3 | /101/102/103 |
| 112 | 101 | 2 | /101/112 |
| 113 | 112 | 3 | /101/112/113 |
| 114 | 113 | 4 | /101/112/113/114 |
+------+-----------+-------+------------------+
6 rows in set (0.01 sec)4.2 sys_connect_by_path … start with id = x
测试语句
select id, father_id, level, sys_connect_by_path(id, ‘/’) as paths from x1
connect by prior id = father_id
start with id = 101;
等价写法：
select id, father_id, 1 as level, concat('|', id, ':1') as pathlevel, concat('/', id) as pathnodesfrom db2.x1 where id = 101union
select id, father_id, level, pathlevel, pathnodes from
(select id, father_id,@le:= if (father_id = 101 , 2, if( locate( concat('|',father_id,':'), @pathlevel) > 0,substring_index( substring_index(@pathlevel,concat('|',father_id,':'),-1),'|',1) +1, -1) ) level,@pathlevel:= if(@le = -1, @pathlevel, concat(@pathlevel,'|',id,':', @le ,'|')) pathlevel,@pathnodes:= if( father_id = 101, concat('/101/', id), concat_ws('/',if( locate( concat('|',father_id,':'),@pathall) > 0 , substring_index( substring_index(@pathall,concat('|', father_id, ':'),-1),'|',1),@pathnodes ) ,id ) )pathnodes,@pathall:=concat(@pathall,'|',id,':', @pathnodes ,'|') pathall from (select id, father_id from db2.x1 where id != 101 order by 1,2)temp1,(select @le := 1,@pathlevel := '|101:1',@pathall:='',@pathnodes:='')temp2
)xxx
where level > 0;测试结果
oracle101 100 1 /101102 101 2 /101/102103 102 3 /101/102/103112 101 2 /101/112113 112 3 /101/112/113114 113 4 /101/112/113/1146 rows selected.mysql 执行结果
+------+-----------+-------+-------------------------------------------+------------------+
| id | father_id | level | pathlevel | pathnodes |
+------+-----------+-------+-------------------------------------------+------------------+
| 101 | 100 | 1 | |101:1 | /101 |
| 102 | 101 | 2 | |101:1|102:2| | /101/102 |
| 103 | 102 | 3 | |101:1|102:2||103:3| | /101/102/103 |
| 112 | 101 | 2 | |101:1|102:2||103:3||112:2| | /101/112 |
| 113 | 112 | 3 | |101:1|102:2||103:3||112:2||113:3| | /101/112/113 |
| 114 | 113 | 4 | |101:1|102:2||103:3||112:2||113:3||114:4| | /101/112/113/114 |
+------+-----------+-------+-------------------------------------------+------------------+
6 rows in set (0.01 sec)
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