PostgreSQL query with CTE giving unexpected result when joining with aggregated data
I'm dealing with After trying multiple solutions online, I still can't figure this out. I tried several approaches but none seem to work. I'm working with an scenario with a PostgreSQL query that uses a Common Table Expression (CTE) to aggregate some data and then join it to another table. I want to count the number of orders per customer and then join that result with customer details to display the total orders alongside each customer's name. However, the counts aren't matching what I expect, and I suspect there's something wrong with my join or aggregation logic. I've tried breaking down the query into simpler parts and verifying each section, but I'm still getting unexpected results. The CTE seems to return the correct counts when run independently, but when joined with the customers table, the results are inflated and not matching the individual customer orders. Here's the SQL query I'm using: ```sql WITH order_counts AS ( SELECT customer_id, COUNT(order_id) AS total_orders FROM orders GROUP BY customer_id ) SELECT c.customer_name, o.total_orders FROM customers c LEFT JOIN order_counts o ON c.id = o.customer_id; ``` In my `orders` table, I have several customers with multiple orders, but it seems like some customers are showing more orders than expected. For instance, Customer A has 3 orders, but the output shows 5 total orders. I also verified that the `customer_id` in the `orders` table is correctly mapped to the `id` in the `customers` table. I’ve confirmed that there are no duplicate entries in the `customers` table, and I'm using PostgreSQL version 14.1. Could anyone guide to understand what might be causing the inflated counts in the join? Are there any common pitfalls with CTEs or joins that I should be aware of? Any ideas what could be causing this? I'm working on a service that needs to handle this. Is there a better approach? I'd love to hear your thoughts on this.