ORACLE 에서 CONNECT BY... START WITH... 의 사용

 、   
    ：select * from some_table [where   1] connect by [  2] start with [  3]; 
   connect by   start with                  ，[where   1]     。 
[where   1]、[  2]、[  3]           ： 

[where   1]    “connect by [  2] start with [  3]”            ，          ，         ； 

[  2]        ，           ，                              ； 

[  3]            ，                      ，                       ； 

  ： 
         ：some_table(id,p_id,name)，  p_id      id。 
select * from some_table t where t.id!=123 connect by prior t.p_id=t.id and t.p_id!=321 start with t.p_id=33 or t.p_id=66; 

 prior   ： 
    prior   [  2] ，    ，            “start with [  3]”   ，             。         ：connect by prior t.p_id=t.id   connect by t.p_id=prior t.id，                  （           ），                  （            ）。 

 、     
connect by...start with...                        RECURSE()      ： 

/*          ，      start with    ，           ， 
             ，    RECURSE()            ， 
                  。*/ 
for rec in (select * from some_table) loop 
if FULLFILLS_START_WITH_CONDITION(rec) then 
    RECURSE(rec, rec.child); 
end if; 
end loop; 

/*           */ 
procedure RECURSE (rec in MATCHES_SELECT_STMT, new_parent IN field_type) is 
begin 
APPEND_RESULT_LIST(rec); /*          */ 
/*           ，      connect by    ，           ， 
              ，    RECURSE()              ， 
            。*/ 
for rec_recurse in (select * from some_table) loop 
    if FULLFILLS_CONNECT_BY_CONDITION(rec_recurse.child, new_parent) then 
      RECURSE(rec_recurse,rec_recurse.child); 
    end if; 
end loop; 
end procedure RECURSE; 

 、     
                “connect by...start with...”       ：（1）         ，                    ，                   。（2）            ，                      ，                   。 
                                   ，                  ，                             
--1.Hierarchical Queries: START WITH and CONNECT BY PRIOR clauses 
--Hierarchical Queries
--START WITH and CONNECT BY PRIOR clauses.

SELECT employee_id, manager_id, first_name, last_name
FROM employee_jh
START WITH employee_id = 1
CONNECT BY PRIOR employee_id = manager_id;

EMPLOYEE_ID MANAGER_ID FIRST_NAME LAST_NAME
----------- ---------- ---------- ----------

          1          0 James      Smith
          2          1 Ron        Johnson
          3          2 Fred       Hobbs
          5          2 Rob        Green
          4          1 Susan      Jones
          6          4 Jane       Brown
          9          6 Henry      Heyson
          7          4 John       Grey
          8          7 Jean       Blue
         10          1 Kevin      Black
         11         10 Keith      Long
         12         10 Frank      Howard
         13         10 Doreen     Penn

13 rows selected.

--2.Using a Subquery in a START WITH Clause
SELECT LEVEL,
       LPAD(' ', 2 * LEVEL - 1) || first_name || ' ' || last_name AS employee
FROM employee_jh
START WITH employee_id = (SELECT employee_id FROM employee_jh WHERE first_name = 'Kevin' AND last_name = 'Black')
CONNECT BY PRIOR employee_id = manager_id;

     LEVEL EMPLOYEE
---------- -------------------------
         1  Kevin Black
         2    Keith Long
         2    Frank Howard
         2    Doreen Penn

--3.Including Other Conditions in a Hierarchical Query
SELECT LEVEL,
       LPAD(' ', 2 * LEVEL - 1) || first_name || ' ' ||
       last_name AS employee, salary
FROM employee_jh
WHERE salary <= 50000
START WITH employee_id = 1
CONNECT BY PRIOR employee_id = manager_id;

     LEVEL EMPLOYEE                      SALARY
---------- ------------------------- ----------
         3      Rob Green                 40000
         3      Jane Brown                45000
         4        Henry Heyson            30000
         3      John Grey                 30000
         4        Jean Blue               29000
         3      Keith Long                50000
         3      Frank Howard              45000
         3      Doreen Penn               47000

8 rows selected.



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