Introduction and normalization Flashcards
An entity type represents more than one business concept. True or false?
False
Normalization reduces data redundancy. True or False
True
Normalization increases the risk of losing data integrity. True or false?
False
A many-to-many relationship can be resolved by using a linking table. True or false?
True
Is the following definition totally correct? “An entity type is in 2NF when all of its non-key attributes are fully dependent on its primary key”
False
About the 1NF (one or more can be selected):
a) each cell in the table can have only one value
b) each cell in the table can have only one value, except for numerical values
c) each cell in the table can have only one value, except for characters values
d) it is possible to have more than one value, as long as the values are separated by a semicolon
e) none of the above
a)
If an entity type is in 3NF, then (one or more can be selected):
a) all attributes are functionally dependent on the primary key
b) all attributes are transitively dependent on the primary key
c) all attributes are not transitively dependent on the primary key
d) complies with the 1NF, but not necessarily with the 2NF
e) none of the above
a) and c)
What is a database?
is a collection of related data items within a specific business process or problem setting.
What is a database management system?
is a software package used to define, create, use, and maintain a database.
What is a database system?
Is the combination of a database and a database management system.
What are the steps of a database design process?
- database requirements
- conceptual data model
- logical data model
- internal data model
Describe the steps of a database design process.
- Database requirements: the aim is to understand the different steps and data needs of the process. Techniques: interviews, surveys, inspections of documents, etc.
- The information architect and the business user formalize the requirements in a conceptual data model. This is a high-level model, easy to understand for the business user and formal enough for the database designer who will use it in the next step.
- The logical data model is based upon the implementation environment. At this stage it is already known what type of DBMS (RDBMS, OODBMS) will be used, the product itself has not been decided yet (Microsoft, IBM, Oracle)
- The logical data model can be mapped to an internal data model by the database designer. In this step, the DBMS product is known. The database can then be populated with data and ready for use.
What is an entity type?
Is a business concept with an unambiguous meaning to a particular set of users. Is anything
that might deserve its own table in the database model.
What is an entity?
Is one particular occurrence or instance of an entity type.
What is an attribute type?
Represents a property of an entity type. Example: name, address are attribute types of the entity type supplier
What is an attribute?
Is an instance of an attribute type.
What is a relationship?
Is an association between two or more entities.
What is a relationship type?
Is a set of relationships among instances of one, two, or more entity types.
What are the three types of cardinalities in relationships?
- Many to many
- One to one
- One to many
What is normalization?
Is a process of analyzing the given relations to ensure they do not contain any redundant data. Is a step-by-step procedure. Can be seen as filters: the more filters applied the better the database, but more complex the database structure.
What is the goal of normalization?
Is to ensure that no anomalies can occur during data insertion, deletion, or update.
What are the three normal forms?
- The 1NF states that every attribute type must be atomic and single-valued. Hence, no composite or multi-valued attribute types are tolerated.
- An entity type is in 2NF when it is in 1NF and when all of its non-key attributes are fully functionally dependent on its primary key.
- An entity type is in 3NF when it is in 2NF and no non-key attribute is transitively dependent on the primary key.
What is the first normal form?
When it contains no repeating groups of data: each cell in the table can have only one value, never a list of values.
Explain functional dependency.
There are two types of functional dependency: full and partial.
A full functional dependency (X -> Y) if the removal of any attribute type A from X means that the dependency does not hold anymore.
A partial functional dependency (X -> Y) is if an attribute type A from X can be removed from X and the dependency still holds.
