How to Efficiently Identify the Top N Maximum Values in MySQL?

Identifying the Top N Max Values in MySQL

In many scenarios, querying for the top N rows with the highest values in a specific column is crucial. However, there can be confusion regarding how to handle cases where multiple rows share the same maximum value and whether to include all rows with the same value or only the top N.

To address this issue, you can utilize the following methods:

Option 1: Exact Top N

Using the LIMIT clause, you can retrieve the exact top N rows in descending order by value, excluding any rows with the same value:

SELECT *
FROM t
ORDER BY value DESC
LIMIT N

Option 2: Inclusive Top N

If you want to include all rows with the same maximum value, even if there are more than N rows with that value, you can use the following approach:

Join the table with a subquery that finds the minimum cutoff value for the top N:

SELECT *
FROM t
JOIN (
  SELECT MIN(value) AS cutoff
  FROM (
    SELECT value
    FROM t
    ORDER BY value
    LIMIT N
  ) tlim
) tlim ON t.value >= tlim.cutoff

Alternatively, you can use a simplified version:

SELECT *
FROM t
JOIN (
  SELECT value
  FROM t
  ORDER BY value
  LIMIT N
) tlim ON t.value = tlim.value

Conceptual Alternative (Optional)

While the following query conceptually captures the desired behavior, it may not work in MySQL:

SELECT *
FROM t
WHERE t.value >= ANY (SELECT value FROM t ORDER BY value LIMIT N)

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