Question

I have 2 tables: Customers and Orders. A customer has many orders and an order belongs to a customer. The order can be approved (marked by a field approved_at).
I want to retrieve all the customers without any approved order. This includes customers without any order and customers with orders that aren’t approved (approved_at = null).
Can I do this in a single query without subqueries?

Answer 1

SELECT ..., COUNT(Orders.id) AS cnt
FROM Customers
LEFT JOIN Orders ON (Customers.id = Orders.Customer_id) AND (Orders.approved_at is null)
HAVING cnt = 0