When two database tables are linked, one of them must have a foreign key that refers to the primary key of another table. A database entity is a person, place, thing, object, or any other item about which data is kept in the database in strict terms.
There are 3 different types of relations in the database:
Database connections are associations between tables that are built by retrieving data using join statements.
A database is a collection of interconnected data. These data are kept in tables that are coupled to one another, and queries are used to search and retrieve data. A table is made up of rows and columns, and it stores data from databases.
Right-click in the Table Designer and select Relationships from the shortcut menu for the table containing the foreign key you want to examine. Select the relationship with properties you want to see in the Foreign Key Relationships dialogue box.