Contrast the navigational databases with relational databases. What is the primary advantage of the relational model?
The most apparent difference between the relational model and navigational models is the way that data associations are represented to the user. In navigational models, data are represented in tree structures or network structures. The navigational database models have explicit links, called pointers, between records. Data are accessed using defined data paths.
The relational model portrays data in the form of two-dimensional tables. Users do not perceive any pointers linking the tables. At the conceptual level (logical view) and the external level (user's view), data are represented only as tables. Relations between tables are formed by an attribute (data element) that is common to the tables. This attribute is a primary key in one table and a foreign key in the other.
The relational model is more flexible than a navigational model. Users can obtain data from the database by using the primary key and a database query language. Typically users do not require assistance from programmers to obtain answers to ad hoc queries.
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