Unexpected Duplicate Rows When Using LEFT JOIN with PostgreSQL 13.3
Does anyone know how to I'm encountering unexpected duplicate rows in my results when executing a LEFT JOIN in PostgreSQL 13.3. I have two tables, `orders` and `customers`, where each order is linked to a customer. The problem arises when a customer has multiple orders; my query returns multiple rows for the same customer, leading to duplicate customer information in the result set. Here’s my current query: ```sql SELECT c.customer_id, c.name, o.order_id, o.amount FROM customers c LEFT JOIN orders o ON c.customer_id = o.customer_id; ``` This returns more rows than anticipated, as I expected one row per customer, even if they have multiple orders. I considered using `DISTINCT`, but that still wouldn’t solve the problem of having order details alongside the customer info. I also tried grouping the results, but it seemed to complicate the output I needed. When I run the query, I get results like this: ``` customer_id | name | order_id | amount -------------|------------|----------|-------- 1 | Alice | 101 | 250.00 1 | Alice | 102 | 150.00 2 | Bob | NULL | NULL 3 | Charlie | 103 | 300.00 ``` As seen, Alice appears twice due to having two separate orders. My goal is to still see all orders for each customer without duplicating the customer information itself. I’ve explored window functions and subqueries, but I’m unsure how best to implement them in this context. Is there a recommended approach to restructure this query to avoid duplicate customer rows while still retrieving order details? Any help would be greatly appreciated! Thanks for any help you can provide! This is my first time working with Sql 3.9. I'd be grateful for any help.