Interview Questions - DBMS

A data type should be selected so that all possible values are represented using minimal storage space. The data type should help to ensure data integrity and support all possible data manipulations (i.e., cannot place a letter in a field such as salary where a number is required).

A unique primary index is unique and is used to find and store a row. A nonunique primary index is not unique and is used to find a row but also where to store a row (based on its unique primary index). A unique secondary index is unique for each row and used to find table rows. A nonunique secondary index is not unique and used to find table rows.

Denormalization is the process of taking normalized relations and changing them so that they are not longer normalized. This process may lead to anomalies and create data redundancy as negative consequences. However, the revised relations should improve database performance.

The hierarchical model is a top-down structure where each parent may have many children but each child can have only one parent. This model supports one-to-one and one-to-many relationships. The network model can be much more flexible than the hierarchical model since each parent can have multiple children but each child can also have multiple parents. This model supports one-to-one, one-to-many, and many-to-many relationships.