Rdms, phase2 db1 Essay Example | Topics and Well Written Essays - 500 words

Rdms, phase2 db1 - Essay Example Two types of integrity constraints entity integrity and referential integrity are taken in account for the design and development of database system. â€Å"An Entity is commonly thought of as a noun – a person, place or thing. In a real sense, Entities reflect Tables in the database† (Mickler, 2008). Entity integrity guarantees that there are no duplicate records within the table and that the field that identifies each record within the table is unique and never null. In general, Entity Integrity is the mechanism the system provides to maintain primary keys so that there is a unique identifier for rows in the table (database.dev.co.uk, 2008). It is good practice to have primary key in every table so that each row can be identified uniquely. â€Å"A primary key is typically only one field and that field is set to a special domain, or type† (Mickler, 2008). A primary key, composed of one or more columns, uniquely identifies each row of a table and eliminates the possibility of duplicate rows in a table (CTU Online, 2008). According to Hoffer, Prescott & McFadden (2007), â€Å"A foreign key is an attribute in a relation of a database that serves as the primary key of another relation in the same database†. Referential integrity maintains the consistency among the rows of two relations. The referential integrity rule states that for every foreign key value in a table, there must be a corresponding primary key value in another table in the database (CTU Online, 2008). Problems arise when we fail to relate the tables properly and inadvertently delete data in a particular table that would result in broken links or floating records (Mickler, 2008). For the new Student Class Registration System we have to make sure that entity and referential integrity constraints are applied. Entity integrity can be achieved by having a primary key not null field in each table of the database system that uniquely identifies each row. In case of our new Student Class Registration