hi everybody! :)
I have 4 tables in my mysql database as

user
car_description
techniqual_description
saled_serial_numbers

In user table user_name is the primary key.

In car_description there is car_id as primary key and serial_number as foreign key which is primary key in table saled_serial number and user_name as foreign key which is primary key in table user.

In techniqual_description car_id is foreign key which is the primary key in table car_description.

My problem is how to insert data in foreign key of tables using C.