sql realizes cascade query of ORACLE database

Using sql to implement cascade query in ORACLE database

select *                 // field to query

from table               //table with child contact ID and parent contact ID 

start with selfid=id       //Given a startid (the field name is the sub-contact ID, and the starting ID number)

connect by prior selfid=parentid        //The connection condition is that the child joint is equal to the parent joint

 

Take a chestnut and take a look---------""""""

The db data fields are as follows:
task_id task_name parent_task_id       
000001 A 0                                
000002 A_1 000001                        
000005 A_2 000001                          

check sentence:

select t.task_id ,t.task_name ,t.parent_task_id 
from t_task t 
start with task_id='000001'
connect by prior task_id = parent_task_id;

The query structure is:

task_id             task_name         parent_task_id       
000001            A                         0                                
000002            A_1                       000001                        
000005           A_2                      000001 

 

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