LeetCode 1581 Interview SQL Question with Detailed Explanation | Practice SQL

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In this video I solve and explain a 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 is about customers who visited but didn't make any transactions and customers per month and also includes points to keep in mind to develop SQL queries.

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[wishimaunicorn]

WOW, thank you for the super clear explaination!

[GajjalaDeepthi]

We can do this in simple way
SELECT customer_id, count(visit_id) as count_no_trans
FROM Visits
where visit_id not in (SELECT visit_id from Transactions)
GROUP BY customer_id
order by count_no_trans Desc

[factsandlogicsonly]

Good Videos. I have started my leetcode problem solving journey and your videos are well described and easy to follow. Keep up the good work

[PIYUSH-lzzq]

how r we getting customer_id 54 ? he has visited with id 5 and done 3 tranasction !!!

[erichuang]

Hi, Can you explain the Count(v.visit_id) part please? I get everything before that, but what exactly are we counting using this expression, and are we counting from the original visit table, or the table we formed? (Like 4 30 Null Null Null )? Thanks!

[kiantopgun]

why use "Where" and not "Having" ?

[divyanshumnit]

select customer_id, count(customer_id) as count_no_trans
from
(select customer_id
from Visits
where visit_id NOT IN (select distinct(visit_id) from Transactions))a
group by customer_id