#### Customers who have made a purchase in the last 30 days

This technical problem involves writing a SQL query to return all customers who have made a purchase in the last 30 days, as well as the total amount they have spent.

#### Problem

```Write a SQL query that returns all customers who have made a purchase in the last 30 days, and the total amount they have spent.
Example input:
customers table:
id | name | date_of_last_purchase
1 | John | 2020-01-10
2 | Jane | 2020-02-15
3 | Joe | 2019-12-20
4 | Sarah | 2020-03-01
5 | Dave | 2020-03-10
6 | Karen | 2020-03-20
7 | Steve | 2020-01-01
8 | Rachel | 2020-02-01
purchases table:
id | customer_id | amount | purchase_date
1 | 1 | 20 | 2020-01-11
2 | 2 | 50 | 2020-02-16
3 | 3 | 10 | 2019-12-21
4 | 4 | 30 | 2020-03-02
5 | 5 | 40 | 2020-03-11
6 | 6 | 60 | 2020-03-21
7 | 7 | 70 | 2020-01-02
8 | 8 | 80 | 2020-02-02
Example output:
customer_id | name | total_spent
1 | John | 20
2 | Jane | 50
4 | Sarah | 30
5 | Dave | 40
6 | Karen | 60```

#### Solution

This solution is in SQL. Our A.I. can create solutions in multiple languages.
```SELECT c.id, c.name, SUM(p.amount) AS total_spent
FROM customers c
JOIN purchases p ON c.id = p.customer_id
WHERE p.purchase_date >= DATE_SUB(NOW(), INTERVAL 30 DAY)
GROUP BY c.id, c.name
ORDER BY total_spent DESC;```

A.I. Evaluation of the Solution

This solution is complete and solves the problem. It uses a JOIN to combine information from the customers and purchases table and then uses the GROUP BY clause to sum the total amount spent for each customer. The solution also uses the DATE_SUB function to only consider purchases made in the last 30 days.

Evaluated at: 2022-11-27 02:16:18