[SQL] ROOT 아이템 구하기

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정답 쿼리

SELECT I.ITEM_ID, I.ITEM_NAME
FROM ITEM_INFO I
JOIN ITEM_TREE T
    ON I.ITEM_ID = T.ITEM_ID
WHERE I.ITEM_ID IN (
    SELECT ITEM_ID
    FROM ITEM_TREE
    WHERE PARENT_ITEM_ID IS NULL
)
ORDER BY I.ITEM_ID ASC;