Cis 276

Topics: Entity-relationship model, Data modeling, Relational model Pages: 2 (374 words) Published: April 24, 2013
CIS 276
February 5th, 2013
1.What is meant by data redundancy? Data redundancy is a situation that occurs within database systems and involves the unintentional creation of duplicated data that is not necessary to the function of the database. 2.What problems are associated with data redundancy?

3.What is an entity? An entity is a person, place, object, event, or idea for which you want to store and process data. An attribute, field, or column is a characteristic or property of an entity. A relationship is an association between entities. 4.What is an attribute? an attribute refers to a database component, such a table. It can also be considered as a characteristic 5.What is a database? A database is a structure that can store information about multiple types of entities, the attributes of the entities, and the relationships among the entities.

6.What is an example of a one-to-many relationship? A one-to-many relationship between two entities exists when each occurrence of the first entity is related to many occurrences of the second entity and each occurrence of the second entity is related to only one occurrence of the first entity.

7.What is an ER diagram? An entity-relationship (E-R) diagram represents a database visually by using a rectangle for each entity that includes the entity’s name above the rectangle and the entity’s columns inside the rectangle, using a line to connect two entities that have a relationship, and placing a dot at the end of a line to indicate the “many” part of a one-to-many relationship.

8.What is an integrity constraint and why are they used? which is expressed by a set of integrity rules or constraints, refers to the correctness of data. Basically it puts it in a certain subject its correct field. It organizes it 9.What is a primary key? A primary key is a combination of one or more column values in a table that make a row of data unique within a database table. 10.What is the primary key for each table in the Henry Books...
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