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오라클 계층쿼리의 활용 본문

Developement/DataBase

오라클 계층쿼리의 활용

highheat 2015. 3. 6. 14:26

출처 : http://www.gurubee.net/lecture/1903

Oracle10g 부터 CONNECT BY 절에서 제공하는 CONNECT_BY_ROOT, SYS_CONNECT_BY_PATH, CONNECT_BY_ISLEAF 기능에 대해서 알아보자

CONNECT_BY_ROOT

계층구조 쿼리에서 LEVEL이 0인 최상위 로우의 정보를 얻어 올 수 있다.

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SELECT LPAD(' ', 4*(LEVEL-1)) || ename ename, empno,
CONNECT_BY_ROOT  empno "Root empno", level
  FROM emp
 START WITH job='PRESIDENT'
CONNECT BY PRIOR empno=mgr;
 
ENAME                    EMPNO  Root empno     LEVEL
------------------     ------- -----------   -------
KING                      7839    7839           1
    JONES                 7566    7839           2
        SCOTT             7788    7839           3
            ADAMS         7876    7839           4
        FORD              7902    7839           3
            SMITH         7369    7839           4

CONNECT_BY_ISLEAF

계층구조 쿼리에서 로우의 최하위 레벨(Leaf) 여부를 반환한다. 최하이 레벨이면 1, 아니면 0

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SELECT LPAD(' ', 4*(LEVEL-1)) || ename ename, empno,
       CONNECT_BY_ISLEAF "leaf", level
  FROM emp
 START WITH job='PRESIDENT'
CONNECT BY NOCYCLE PRIOR empno=mgr;
 
 
ENAME                     EMPNO       leaf      LEVEL
-------------------- ---------- ---------- ----------
KING                       7839          0          1
    JONES                  7566          0          2
        SCOTT              7788          0          3
            ADAMS          7876          1          4
        FORD               7902          1          3
    BLAKE                  7698          0          2
        MARTIN             7654          1          3
        TURNER             7844          1          3
        JAMES              7900          1          3
    CLARK                  7782          0          2
        MILLER             7934          1          3

SYS_CONNECT_BY_PATH

계층구조 쿼리에서 현재 로우 까지의 PATH 정보를 쉽게 얻어 올 수 있다.

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-- SQL*Plus에서만 깔끔하게 보기위해서
COL PATH FORMAT A40
 
 
-- SYS_CONNECT_BY_PATH 예제
SELECT LPAD(' ', 4*(LEVEL-1)) || ename ename, empno,
       SYS_CONNECT_BY_PATH(ename, '/') "PATH"
  FROM emp
 START WITH job='PRESIDENT'
CONNECT BY PRIOR empno=mgr;
 
 
ENAME                     EMPNO PATH
-------------------- ---------- ---------------------------
KING                       7839 /KING
    JONES                  7566 /KING/JONES
        SCOTT              7788 /KING/JONES/SCOTT
            ADAMS          7876 /KING/JONES/SCOTT/ADAMS
        FORD               7902 /KING/JONES/FORD
    BLAKE                  7698 /KING/BLAKE
        MARTIN             7654 /KING/BLAKE/MARTIN
        TURNER             7844 /KING/BLAKE/TURNER
        JAMES              7900 /KING/BLAKE/JAMES
    CLARK                  7782 /KING/CLARK
        MILLER             7934 /KING/CLARK/MILLER

아래와 같이 Leaf Node만 전체 PATH 정보가 나오도록 작성 할 수 있다

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-- SQL*Plus에서만 깔끔하게 보기위해서
COL PATH FORMAT A40
 
 
SELECT LEVEL, SUBSTR(SYS_CONNECT_BY_PATH(ename, ','), 2) path
  FROM emp
 WHERE CONNECT_BY_ISLEAF = 1
 START WITH mgr IS NULL
CONNECT BY PRIOR empno = mgr;
 
 
    LEVEL PATH
--------- -------------------------
        4 KING,JONES,SCOTT,ADAMS
        3 KING,JONES,FORD
        3 KING,BLAKE,MARTIN
        3 KING,BLAKE,TURNER
        3 KING,BLAKE,JAMES
        3 KING,CLARK,MILLER

ORDER SIBLINGS BY

계층구조 쿼리에서 상관관계를 유지하면서 정렬을 할 수 있게 해준다. 아래 예제를 가지고 ORDER SIBLINGS BY와 ORDER BY로 테스트 해보자

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-- SQL*Plus에서만 깔끔하게 보기위해서
COL ename FORMAT A25
COL ename2 FORMAT A10
 
 
-- ORDER SIBLINGS BY 예
-- 정렬이 정상적으로 수행된 것을 확인 할 수 있다.
SELECT LPAD(' ', 4*(LEVEL-1)) || ename ename,
       ename ename2, empno, level
  FROM emp
 START WITH job='PRESIDENT'
CONNECT BY NOCYCLE PRIOR empno=mgr
 ORDER SIBLINGS BY ename2;
 
 
ENAME                ENAME2          EMPNO      LEVEL
-------------------- ---------- ---------- ----------
KING                 KING             7839          1
    BLAKE            BLAKE            7698          2
        JAMES        JAMES            7900          3
        MARTIN       MARTIN           7654          3
        TURNER       TURNER           7844          3
    CLARK            CLARK            7782          2
        MILLER       MILLER           7934          3
    JONES            JONES            7566          2
        FORD         FORD             7902          3
        SCOTT        SCOTT            7788          3
            ADAMS    ADAMS            7876          4
 
 
 
 
-- ORDER BY 예
-- 정렬이 이상하게 수행된 것을 확인 할 수 있다.
SELECT LPAD(' ', 4*(LEVEL-1)) || ename ename,
       ename ename2, empno, level
  FROM emp
 START WITH job='PRESIDENT'
CONNECT BY NOCYCLE PRIOR empno=mgr
 ORDER BY ename2;
 
 
ENAME                ENAME2          EMPNO      LEVEL
-------------------- ---------- ---------- ----------
            ADAMS    ADAMS            7876          4
    BLAKE            BLAKE            7698          2
    CLARK            CLARK            7782          2
        FORD         FORD             7902          3
        JAMES        JAMES            7900          3
    JONES            JONES            7566          2
KING                 KING             7839          1
        MARTIN       MARTIN           7654          3
        MILLER       MILLER           7934          3
        SCOTT        SCOTT            7788          3
        TURNER       TURNER           7844          3


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