LeetCode 1581: Customer Who Visited but Did Not Make Any Transactions Solution

Master LeetCode problem 1581 (Customer Who Visited but Did Not Make Any Transactions), a easy challenge, with our optimized solutions in Java, C++, and Python. Explore detailed explanations, test your code in our interactive editor, and prepare for coding interviews.

1581. Customer Who Visited but Did Not Make Any Transactions

Easy

Database

Problem Explanation

Explanation:

To solve this problem, we need to identify customers who visited the mall but did not make any transactions. We can achieve this by performing a left join between the Visits and Transactions tables and then filtering out the rows where there is no corresponding transaction.

Perform a left join between the Visits and Transactions tables on the visit_id column.
Filter out the rows where there is no corresponding transaction (i.e., where transaction_id is NULL).
Count the number of such occurrences for each customer_id.
Return the customer_id and the count of visits without transactions.

Time complexity: O(n) Space complexity: O(n)

Solution Code

# Write your Java solution here
SELECT v.customer_id AS customer_id, 
       COUNT(t.visit_id) AS count_no_trans
FROM Visits v
LEFT JOIN Transactions t
ON v.visit_id = t.visit_id
WHERE t.visit_id IS NULL
GROUP BY v.customer_id;

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