PostgreSQL: Why does my query return incorrect row counts when using window functions with multiple PARTITION BY clauses?
Does anyone know how to I've been banging my head against this for hours. I've looked through the documentation and I'm still confused about I'm working on a PostgreSQL 13 database and trying to generate a report that includes a row count for each product category, as well as the total sales for each product within that category... I'm using window functions with `PARTITION BY` clauses to achieve this, but I'm getting unexpected row counts in the results. Here's a simplified version of my query: ```sql SELECT category_id, product_id, sales_amount, COUNT(*) OVER (PARTITION BY category_id) AS category_count, SUM(sales_amount) OVER (PARTITION BY category_id) AS total_sales FROM sales ORDER BY category_id, product_id; ``` When I run this, I expect `category_count` to give me the total number of products in each category, but it seems like it returns the number of rows instead. For example, if I have 5 products in the 'Electronics' category, I expect `category_count` to show 5 for each row of those products. Instead, it sometimes shows 4 for some rows and 5 for others, which doesn't make sense. I've double-checked the data in the `sales` table and confirmed that there are indeed 5 products in the 'Electronics' category. I also tried removing the `SUM` function to see if that resolved the scenario, but the counts still fluctuate. Iām confused about how the window functions are interacting in this case. Could someone explain why this might be happening? Am I misusing the window functions, or is there something else that could be affecting the results? Any help would be greatly appreciated! This is part of a larger application I'm building. Thanks in advance! This is part of a larger web app I'm building. What am I doing wrong? I'm working with Sql in a Docker container on Linux. How would you solve this?