Question

What is the significance of the constraints in a physical model? What part do distinct constraints play in preserving referential integrity and data integrity?

Answer 1

Answer)
The physical data model is the representation of the data on which the database will be built. The physical model is the database model which is used to show the table structures, column names, data types and also the constraint such as the primary keys and foreign keys and thus depict the relationship between the tables. The significance of the constraints in a physical model means that the constraints such as the referential integrity and data integrity, using the primary keys and foreign keys are used to identify the relationship between the tables and are thus important.
The unique or the distinct constraints are the constraints which mean that the column or set of columns can accept only the unique data values and thus duplicate values and data are not accepted in those columns. These are especially required in the preserving of referential integrity and data integrity. The referential integrity means that the data should be accurate and consistent, and this is done by having a foreign key referencing the primary keys in the tables. The data integrity is thus the maintaining of the accuracy and the consistency of the data and is this important.