DBMS - Interview Questions and Answers
Briefly describe the six database activities that occur during the systems development life cycle.
The enterprise modeling that analyzes the current data processing. Conceptual data modeling that identifies entities, relationships, and attributes. The logical database design that identifies data integrity and security requirements. The physical database design and definition that defines the database to a DBMS. The database implementation that installs and converts data from prior systems. Database maintenance that fixes errors in the database and database applications.
Briefly explain an ERD.
An ERD is a detailed logical representation of the data for an organization. The ERD includes entities, attributes, relationships, and cardinalities. An ERD is the mechanism where an entity-relationship model is displayed.
List some of the chrematistics of good data definitions.
Definitions are gathered from the same sources and should be accompanied diagrams. A definition will include special conditions, examples, how the data is created, whether the data can change, who owns the data, whether the data is optional, and whether the data can be broken into something more atomic.
Explain minimum and maximum cardinality.
Minimum cardinality is the minimum number of instances of an entity that can be associated with each instance of another entity. Maximum cardinality is the maximum number of instances of an entity that can be associated with each instance of another entity.
Describe the naming of Relationships?
Relationships are verb phrases and represent actions usually in the present tense. The name should exclude vague names such as "has". The name should explain what action is being taken and possibly why it is important.
Why is modeling time-dependent data with a time stamp important?
The values of data may change. A time stamp helps to ensure that the previous value of the data stays in the database after it has changed so that you can see the before and after values through time. Without a time stamp, you will most likely lose some of the history.