【oracle】樹狀結構查詢
[sql]
--oracle中的樹狀結構查詢實際上就是乙個中序遍歷
--顯示以king為根節點的樹，start with定義起始節點
select *
from emp a
start with a.empno = 7839
connect by prior a.empno = a.mgr;
--置於等號前面，由父節點向子節點方向檢索；置於等號後面，則從子節點向父節點方向檢索
select *
from emp a
start with a.empno = 7839
connect by prior a.empno = a.mgr;
--使用偽列level來顯示層級關係
select *
from emp a
start with a.empno = 7839
connect by prior a.empno = a.mgr;
select level, a.*
from emp a
start with a.empno = 7839
connect by prior a.empno = a.mgr;
--使用函式 sys_connect_by_path 顯示全路徑
select level, sys_connect_by_path(a.ename, '/'), a.*
from emp a
start with a.empno = 7839
connect by prior a.empno = a.mgr;
--where子句只限定單個節點，不影響子其子節點或者父節點
select level, sys_connect_by_path(a.ename, '/'), a.*
from emp a
where a.empno <> 7369
start with a.empno = 7839
connect by prior a.empno = a.mgr;
--connect by 子句限定整個以當前節點為起始節點的整個分支
--connect_by_root 可以在列之前顯示最高節點的內容
select level, connect_by_root(a.job),sys_connect_by_path(a.ename, '/'), a.*
from emp a
where a.empno <> 7369
start with a.empno = 7839
connect by prior a.empno = a.mgr;
--connect_by_isleaf 顯示當前行是否葉子節點，1：是；0：否
select level, connect_by_isleaf,sys_connect_by_path(a.ename, '/'), a.*
from emp a
where a.empno <> 7369
start with a.empno = 7839
connect by prior a.empno = a.mgr;
--connect_by_iscycle 10g中開始有的新特性，用來判斷當前節點是否產生了迴圈，0：否；1：是
select level, connect_by_iscycle, connect_by_isleaf,sys_connect_by_path(a.ename, '/'), a.*
from emp a
where a.empno <> 7369
start with a.empno = 7839
connect by nocycle prior a.empno = a.mgr;
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