Unexpected Null Values in Aggregation with LEFT JOIN in PostgreSQL 13
I've looked through the documentation and I'm still confused about I'm working on a project and hit a roadblock. I'm working with an scenario with unexpected null values appearing in my aggregated results when performing a LEFT JOIN between two tables in PostgreSQL 13. I have two tables, `orders` and `customers`, where I'm trying to get a count of orders for each customer. However, customers with no orders are returning null instead of a count of zero in my result set. Here's the SQL query I'm using: ```sql SELECT c.id, c.name, COUNT(o.id) as order_count FROM customers c LEFT JOIN orders o ON c.id = o.customer_id GROUP BY c.id, c.name; ``` I expected to see all customers listed with a count of orders, including those without any orders, but instead, the `order_count` for customers with no orders is showing up as null. I tried using `COALESCE` to handle the null values like this: ```sql SELECT c.id, c.name, COALESCE(COUNT(o.id), 0) as order_count FROM customers c LEFT JOIN orders o ON c.id = o.customer_id GROUP BY c.id, c.name; ``` However, this doesn't resolve the scenario, and I'm still seeing null values in the `order_count`. I've also checked that there are indeed customers without orders by running a simple query on the `customers` table. Is there something I'm missing in my SQL syntax or logic? Why are the counts not defaulting to zero for customers without orders? Any insights into this behavior would be greatly appreciated! I'm working on a API that needs to handle this. How would you solve this? This is my first time working with Sql LTS. Any feedback is welcome!