Tree Node.md

⚙문제보기

🔎문제 풀이 MySQL

SELECT
    id, 'Root' AS Type
FROM
    tree
WHERE
    p_id IS NULL

UNION

SELECT
    id, 'Leaf' AS Type
FROM
    tree
WHERE
    id NOT IN (SELECT DISTINCT
            p_id
        FROM
            tree
        WHERE
            p_id IS NOT NULL)
        AND p_id IS NOT NULL

UNION

SELECT
    id, 'Inner' AS Type
FROM
    tree
WHERE
    id IN (SELECT DISTINCT
            p_id
        FROM
            tree
        WHERE
            p_id IS NOT NULL)
        AND p_id IS NOT NULL
ORDER BY id;

OR MySQL

SELECT id,
CASE 
    WHEN p_id IS NULL THEN 'Root'
    WHEN id IN (SELECT p_id FROM Tree WHERE p_id IS NOT NULL) THEN 'Inner'
    ELSE 'Leaf' 
    END AS 'type'
FROM Tree

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다른 사람 풀이 어떻게 하는지 참고함.