LeetCode Medium 1990 'Number of Experiments' Twitter Interview SQL Question Detailed Explanation

In this video I solve and explain a medium difficulty leetcode SQL question using MySQL query. This question has been asked in Apple, Facebook, Amazon, Google, Adobe, Microsoft, Adobe interviews or what we popularly call FAANG interviews.
I explain the related concept as well. This question includes points to keep in mind to develop SQL queries.

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[praneethreddy]

Hi, useful videos.. thank you.. one question- we are hard coding the values and union them to list the all platform or experiment names; here the values are 3, but if we have more values, we can’t hardcode all the values and the code will be cumbersome.. could you please tell the alternative way

[ujjwalvarshney]

select distinct a.platform, distinct b.experiment_name from experiment 1 cross join experiment b will work or not

[sachindewangan]

Bro, instead of using another cte you could've done this:

WITH cte AS
(SELECT *
FROM (SELECT "Android" AS platform UNION SELECT "IOS" UNION SELECT "Web") t1
CROSS JOIN
(SELECT "Reading" AS experiment_name UNION SELECT "Sports" UNION SELECT "Programming") t2)

SELECT c.*, IFNULL(COUNT(e.experiment_id), 0) AS num_experiments
FROM cte c
LEFT JOIN Experiments e
ON c.platform = e.platform AND c.experiment_name = e.experiment_name
GROUP BY c.platform, c.experiment_name