Free Custom «Relational Database Management» Essay Paper

Entity and referential are rules concerning integrity or database concepts. Entity is an integrity that referential integrity is based on. It is a rule that says that each table should posses a primary key. It also states that all columns which are chosen to be primary keys should be special and different but not illogical. A more straight consequence of this kind of rule is that copied rows are not allowed in a table and that no copied rows can appear logically inside the table if all values of a main key should remain distinctive (Levene, 1999). It ensures a rate can be used in identifying each row in the table. In other words, the entity rule rejects any duplicated primary key and makes sure that one stores proper format of data. It is important in relational database because it does not allow invalid primary key. For example, we can have a student's table with student's number. The column for students remains a unique system that generates the number of students in all rows in the table (Date, 1988).Referential integrity refers to a database rule which makes sure that the table relationships remain constant. That is, if any table has a different key compared to another table then there are no possibilities to add a record to the table containing the foreign key. These rules also involve the update and delete cascading techniques that make sure the changes that are made to the related table are shown in the primary table. It is based on the entity integrity. It is important in rational database because it ensures that all coupled tables are consistent. For instance one can possibly define models with entity types like students, student Line. Student line is the key with a value from a related entity of the type Students. Therefore both referential and entity systems of integrity are related and important to relational database (Levene, 1999).