PostgreSQL: advanced patterns with CTEs and Interleaved SELECT Statements
I tried several approaches but none seem to work. I'm running into a puzzling scenario with Common Table Expressions (CTEs) in PostgreSQL 13. When I use a CTE followed by an interleaved SELECT statement, I get unexpected results. Specifically, I have a CTE that calculates a running total of orders, and I'm trying to filter for orders over a specific amount after using the CTE, but it doesn't seem to work as expected. Here's the relevant portion of my query: ```sql WITH RunningTotal AS ( SELECT order_id, amount, SUM(amount) OVER (ORDER BY order_id) AS running_total FROM orders ) SELECT * FROM RunningTotal WHERE running_total > 5000; SELECT * FROM RunningTotal WHERE amount < 100; ``` The first part of the query returns the expected results, showing orders with a running total greater than 5000. However, the second SELECT statement, which references the same CTE, is not returning any results, even though there are orders with amounts less than 100. I’ve checked that there are orders in the `orders` table that meet this condition, and I suspect it might be related to how the CTE is scoped or executed in PostgreSQL. I've also tried using `SELECT * FROM orders WHERE amount < 100`, and that works fine, so the scenario seems to be specific to the CTE. Is there something I’m missing in terms of how CTEs work in this context? Any insights would be greatly appreciated.