[DATABASE/SQLSERVER] CTE 재귀 호출 사용하기

■ CTE 재귀 호출을 사용하는 방법을 보여준다.

▶ 예제 코드 (SQL)


CREATE TABLE MENU
(
    ID        INT
   ,PARENT_ID INT
   ,NAME      VARCHAR(50)
);

INSERT INTO MENU VALUES (1, 0, '메뉴');
INSERT INTO MENU VALUES (2, 0, '메뉴');
INSERT INTO MENU VALUES (3, 1, '메뉴');
INSERT INTO MENU VALUES (4, 1, '메뉴');
INSERT INTO MENU VALUES (5, 1, '메뉴');
INSERT INTO MENU VALUES (6, 5, '메뉴');
INSERT INTO MENU VALUES (7, 2, '메뉴');
INSERT INTO MENU VALUES (8, 2, '메뉴');

WITH CTE(ID, PARENT_ID, NAME, DISPLAY_ORDER, TREE_PATH)
AS
(
    SELECT
        ID
       ,PARENT_ID
       ,NAME
       ,CONVERT(VARCHAR(4000), ID  ) AS DISPLAY_ORDER
       ,CONVERT(VARCHAR(4000), NAME) AS TREE_PATH
    FROM MENU
    WHERE PARENT_ID = 0
    UNION ALL
    SELECT
        A.ID
       ,A.PARENT_ID
       ,A.NAME
       ,CONVERT(VARCHAR(4000), B.DISPLAY_ORDER + ' > ' + CONVERT(VARCHAR(4000), A.ID)) AS DISPLAY_ORDER
       ,CONVERT(VARCHAR(4000), B.TREE_PATH     + ' > ' + A.NAME                      ) AS TREE_PATH
    FROM  MENU AS A, CTE AS B
    WHERE A.PARENT_ID = B.ID
)
SELECT
    NAME
   ,TREE_PATH
FROM CTE
ORDER BY DISPLAY_ORDER;

CREATE TABLE MENU

(

ID INT

,PARENT_ID INT

,NAME VARCHAR(50)

);

INSERT INTO MENU VALUES (1, 0, '메뉴');

INSERT INTO MENU VALUES (2, 0, '메뉴');

INSERT INTO MENU VALUES (3, 1, '메뉴');

INSERT INTO MENU VALUES (4, 1, '메뉴');

INSERT INTO MENU VALUES (5, 1, '메뉴');

INSERT INTO MENU VALUES (6, 5, '메뉴');

INSERT INTO MENU VALUES (7, 2, '메뉴');

INSERT INTO MENU VALUES (8, 2, '메뉴');

WITH CTE(ID, PARENT_ID, NAME, DISPLAY_ORDER, TREE_PATH)

(

SELECT

,PARENT_ID

,NAME

,CONVERT(VARCHAR(4000), ID ) AS DISPLAY_ORDER

,CONVERT(VARCHAR(4000), NAME) AS TREE_PATH

FROM MENU

WHERE PARENT_ID = 0

UNION ALL

SELECT

A.ID

,A.PARENT_ID

,A.NAME

,CONVERT(VARCHAR(4000), B.DISPLAY_ORDER + ' > ' + CONVERT(VARCHAR(4000), A.ID)) AS DISPLAY_ORDER

,CONVERT(VARCHAR(4000), B.TREE_PATH + ' > ' + A.NAME ) AS TREE_PATH

FROM MENU AS A, CTE AS B

WHERE A.PARENT_ID = B.ID

)

SELECT

NAME

,TREE_PATH

FROM CTE

ORDER BY DISPLAY_ORDER;