[leetcode]1211. Queries Quality and Percentage

문제

https://leetcode.com/problems/queries-quality-and-percentage/description/?envType=study-plan-v2&envId=top-sql-50

풀이 코드

SELECT
    query_name,
    ROUND(SUM(rating / position) / COUNT(*) ,2) as quality,
    ROUND(SUM(CASE WHEN rating<3 THEN 1 ELSE 0 END)/COUNT(*)*100,2) AS poor_query_percentage
FROM
    Queries
WHERE 1=1
    AND query_name IS NOT NULL
GROUP BY
    query_name

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후기

왜 query_name에 null값이 있는지 이해가 안됨..