INNER JOIN in MySQL - mysql

Question

There are my two tables:
Table name: FRIENDS
+-------+---------+---------+-------------------+
| id | firstName | lastName | city |
+-------+--------------+------------+-----------+
| 1 | dudi | edri | london |
| 2 | maor | azulay | madrid |
| 3 | batel | azulay | tel aviv |
| 4 | nir | cohen | barcelona |
| 5 | evia | perez | miami |
| 6 | neria | perez | new-york |
| 7 | nevo | kakoun | roma |
+-------+---------+---------+-------------------+
Table name: ORDERS
+-------+---------+---------+-----------------+
| id | firstName | amount | status |
+-------+--------------+----------+-----------+
| 1 | dudi | 5684 | shipped |
| 2 | maor | 4896 | shipped |
| 3 | batel | 2496 | delay |
+-------+--------------+----------+-----------+
my question is:
I want the friends that have no order.
The answer:
| 4 | nir | cohen | barcelona |
| 5 | evia | perez | miami |
| 6 | neria | perez | new-york |
| 7 | nevo | kakoun | roma |
+-------+---------+---------+-------------------+
how i wrote the query with inner join.
Thanks.

Answer 1

You shouldn't use firstName in ORDERS as Foreign Key. The foreign key should reference the primary key. Use ID from FRIENDS like:
Table name: ORDERS
+-------+---------+---------+-----------------+
| id | friendID | amount | status |
+-------+--------------+----------+-----------+
| 1 | 1 | 5684 | shipped |
| 2 | 2 | 4896 | shipped |
| 3 | 3 | 2496 | delay |
+-------+--------------+----------+-----------+
And query using LEFT OUTER JOIN:
SELECT f.*
FROM FRIENDS f
LEFT JOIN ORDERS o
ON f.ID = o.friendID
WHERE o.ID IS NULL;
LiveDemo
Another possibility is to use correlated subquery:
SELECT f.*
FROM FRIENDS f
WHERE NOT EXISTS (SELECT 1
FROM orders o
WHERE o.friendID = f.ID);
LiveDemo2
Tables:
CREATE TABLE friends(
id INTEGER NOT NULL PRIMARY KEY -- you can add AUTO_INCREMENT if needed
...
);
CREATE TABLE orders(
id INTEGER NOT NULL PRIMARY KEY
,friendID INTEGER NOT NULL
,FOREIGN KEY (friendID) REFERENCES friends(id)
...
);