This relates to one aspect of data integrity. Data across multiple tables are linked via relationships. In view of the distinct customer & invoice tables, each invoice table should have the primary key specified throughout the Customer table, for instance. Whenever the invoice table contains a customer ID reference. This ID including its customer will be only a table of the customer.
yes. Look up popular video repair sites and download it (unless its online) but dont just go clicking on random things you dont want to give yourself a virus XD
