SQL Server: implementing DATEADD and Multiple Conditions in WHERE Clause Leading to Incorrect Time Adjustments
I'm performance testing and I'm migrating some code and I'm working with an scenario with a SQL Server query that uses the `DATEADD` function along with multiple conditions in the `WHERE` clause..... The intention is to filter records based on a dynamic date range, but I'm getting unexpected results where certain rows are excluded even though they should be included based on the conditions. My query looks like this: ```sql SELECT * FROM Orders WHERE OrderDate >= DATEADD(DAY, -7, GETDATE()) AND (CustomerID IN (SELECT CustomerID FROM Customers WHERE Status = 'Active') OR OrderAmount > 100) ``` In this query, I want to fetch orders from the last 7 days for active customers or orders that exceed $100. However, I'm noticing that some valid orders within the date range are not being returned. I’ve tried breaking down the `WHERE` clause and running it in segments to verify the logic: ```sql SELECT * FROM Orders WHERE OrderDate >= DATEADD(DAY, -7, GETDATE()) ``` This part returns the expected results, including all relevant orders in the last week. Then I checked the active customers: ```sql SELECT CustomerID FROM Customers WHERE Status = 'Active' ``` This returns a valid list of active customers. However, when I reintroduce the second condition in the main query, I start getting missing orders that should match both conditions. I suspect the way I'm combining the `OR` statement might be causing the scenario, as it could be filtering out records unintentionally. The SQL Server version I’m using is 2019. Any insights on how to approach this question or best practices for handling multiple conditions in the `WHERE` clause would be greatly appreciated! Also, if there's a better way to structure this query for performance, I’d love to hear it. Thanks! Any advice would be much appreciated. Has anyone else encountered this?