LeetCode 1581: Customer Who Visited but Did Not Make Any Transactions
LeetCode 1581 Solution 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
VisitsandTransactionstables on thevisit_idcolumn. - Filter out the rows where there is no corresponding transaction (i.e., where
transaction_idis NULL). - Count the number of such occurrences for each
customer_id. - Return the
customer_idand the count of visits without transactions.
Time complexity: O(n) Space complexity: O(n)
:
LeetCode 1581 Solutions in Java, C++, Python
# 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;Interactive Code Editor for LeetCode 1581
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