The Problem

The challenge involves the table World.

World table:

Each row of this table provides information about a country, including its continent, area, population, and GDP. We define a country as "big" if it has an area of at least 3 million km2 or a population of at least 25 million.

The task is to write an SQL query that reports the name, population, and area of the "big" countries.

Explanation

Here's an example for better understanding:

Input:

World table:

Output:

Afghanistan and Algeria are considered "big" countries as their population or area exceeds the defined thresholds.

The Solution

Let's explore two SQL solutions to this problem, examining their differences, strengths, and weaknesses.

Source Code 1

The first solution retrieves countries from the table where the area is at least 3 million or the population is at least 25 million.

SELECT
    name,
    population,
    area
FROM
    World
WHERE
    area >= 3000000
    OR
    population >= 25000000

This query achieves a runtime of 904ms, outperforming 92.98% of other submissions.

Source Code 2

The second solution is very similar to the first, but it first checks for the population condition before the area condition.

SELECT
    name,
    population,
    area
FROM
    World
WHERE
    population >= 25000000
    OR
    area >= 3000000

This query has a runtime of 983ms, beating 78.89% of other submissions.

Conclusion

Both solutions yield the same output but have minor performance differences due to the order of conditions in the WHERE clause. Thus, the ranking of solutions based on overall performance, from best to worst, is: Source Code 1 > Source Code 2.

You should choose the solution that best fits your specific performance requirements and expectations.

You can find the original problem at LeetCode.

For more insightful solutions and tech-related content, connect with me on my Beacons page.

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