We have a table called score with two columns: ball (ball number) and score (score made on that ball). How would you calculate the average score per over?

Assuming the table score has columns ball (integer) and score (integer), you can compute the average score per over using integer division to derive the over number. In SQL:

SELECT ((ball - 1) / 6) + 1 AS over,
       AVG(score) AS avg_score
FROM score
GROUP BY over
ORDER BY over;

Explanation: (ball - 1) / 6 gives the zero‑based over index because the first six balls belong to over 0. Adding 1 converts it to a 1‑based over number. AVG(score) calculates the mean score for each over. The query runs in O(n) time with a single scan of the table and uses O(k) space for the grouping, where k is the number of overs.