SQL Interview Questions – Unique Orders and Customers Per Month

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Problem Description –

Write an SQL query to find the number of unique orders and the number of unique customers with invoices > $20 for each different month.

Return the result table sorted in any order.

The query result format is in the following example.

Problem Link – unique orders and customers

Difficulty Level – Easy

Solution –

    DATE_FORMAT(order_date, '%Y-%m') as month,
    COUNT(DISTINCT order_id) as order_count,
    COUNT(DISTINCT customer_id) as customer_count
FROM Orders
WHERE invoice > 20

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