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这道题目不难，但是有很多需要考虑的点以及容易写错的地方。 SELECT query_name, ROUND(AVG(rating/position), 2) AS quality, ROUND(SUM(CASE WHEN rating < 3 THEN 1 ELSE 0 END) * 100 / C ......

别急。先更一波T2,T3。 七管荧光灯 可以状压打表可以发现：一种局面为必败状态当且仅当满足 \(a_{1}=x,a_{2}=x,a_{3}=x,a_{4}=y,a_{5}={z},a_{6}=z,a_{7}=z\) 且 \(x \oplus y \oplus z=0\)。 然后就可以数位 dp 了 ......

select query_name, round(avg(rating/position), 2) as quality, round(sum(rating<3)*100/count(query_name), 2) as poor_query_percentage from Queries grou ......

【题目】 查询表 Queries： + + +| Column Name | Type |+ + +| query_name | varchar || result | varchar || position | int || rating | int |+ + +此表没有主键，并可能有重复的行。此 ......