Insert the Wrong Customer Id

Insert a nonexistent customer_id

Let’s see our customers and orders again.

mysql> select * from customers;
+----+-----------+----------+
| id | name      | identity |
+----+-----------+----------+
|  1 | John Woo  | JW0001   |
|  3 | Maria Moo | ML0001   |
+----+-----------+----------+
2 rows in set (0.00 sec)

mysql> select * from orders;
+----+--------------+---------------------+-------------+
| id | order_number | ordered_at          | customer_id |
+----+--------------+---------------------+-------------+
|  1 | ABC001       | 2016-09-09 08:34:55 |           1 |
+----+--------------+---------------------+-------------+
1 row in set (0.00 sec)

The order with an id of 1 refers to the customer with id of 1 via the customer_id column. Let’s try to insert a new order that references a nonexistent customer. Try the following command: