SQL Server: Unexpected results when using LEFT JOIN with NULL filtering in WHERE clause
I'm working with a question with a SQL Server query where I'm using a `LEFT JOIN`, but the results are not as expected when I filter on a column that can be NULL. I'm trying to retrieve all records from the `Orders` table and their corresponding records from the `Customers` table, including cases where a customer may not exist for a particular order. Here’s the query I've written: ```sql SELECT o.OrderID, o.OrderDate, c.CustomerName FROM Orders o LEFT JOIN Customers c ON o.CustomerID = c.CustomerID WHERE c.CustomerName IS NULL; ``` However, this query returns an empty result set, even though there are orders without associated customers. I expected to see those orders listed with `NULL` for `CustomerName`. I've attempted to modify the WHERE clause to check for `NULL` values in the `Orders` table instead: ```sql WHERE o.CustomerID IS NULL; ``` This resulted in errors, as `CustomerID` in the `Orders` table will never be `NULL` if the order exists. I understand that filtering by a column from the right table in a `LEFT JOIN` can eliminate rows from the result set that should be included when there's no match. Is there a way to properly structure my query to achieve the desired results? I'm using SQL Server 2019. Any insights or recommendations would be greatly appreciated! This issue appeared after updating to Sql latest.