MySQL 8.0 - implementing SELECT query returning NULL instead of expected values when using LEFT JOIN
This might be a silly question, but I'm having trouble with a query where I expect to retrieve data from two tables using a LEFT JOIN, but I'm receiving NULL values in certain columns where I believe there should be valid entries. I'm using MySQL 8.0, and here’s the scenario: I have two tables: `users` and `orders`. The `users` table contains user information, and the `orders` table contains order information. Each user can have multiple orders, but some users do not have any orders yet. Here’s the structure of the tables: ```sql CREATE TABLE users ( id INT PRIMARY KEY, username VARCHAR(50) ); CREATE TABLE orders ( id INT PRIMARY KEY, user_id INT, order_date DATE, FOREIGN KEY (user_id) REFERENCES users(id) ); ``` When I run the following query: ```sql SELECT u.id, u.username, o.order_date FROM users u LEFT JOIN orders o ON u.id = o.user_id; ``` I expect to get a list of all users along with their order dates. For users without orders, the `order_date` should be NULL, which is what I'm seeing. However, I also notice that for some users, the `username` field is NULL, which should not be the case. I've checked the `users` table and confirmed that there are entries for all the users I’m querying. To troubleshoot, I tried running just the `SELECT * FROM users;` query and it returns all expected data correctly. I’ve also verified that there are no spelling errors in the column names in my query. I have a suspicion that there might be something wrong with the way the foreign key is set up or perhaps some unexpected data state. I also tried running the query with `INNER JOIN` instead of `LEFT JOIN`, and it works fine, returning only the users that have orders. What could be causing the `username` to return NULL in this LEFT JOIN query? Is there something wrong with my table setup or my query? Any help would be appreciated! I'd really appreciate any guidance on this.