Car tax (2 files)

This is the base task solution for structures vol 2 lab task where you had to read from two files and associate the data based on the unique key which was product code.

Explanations about keys (PK/FK) - more on this in databases lab

PK (primary key) – Unique field or a pair of fields in a table or a file that identifies a record (row in a file). Quite often an integer is used, but it can be any type that is unique. One file or table can only have a single primary key. Each file or table has to have a primary key.

FK (foreign key) – this is used to create relations to other tables or files. If a foreign key matches the primary key in another file or table, then these items are related to each other. One file or table can have multiple foreign keys and they’re not unique (can repeat within).

Foreign key and primary key form a relation between 2 or more files or database tables. A single primary key in one file can be related to multiple foreign items in the second file.

E.g. one person can have multiple children; one receipt can have multiple products; one student can have multiple subject declarations; One person can own multiple properties;