Midterm Review Flashcards
Chapters 1-6, 9 main concepts review (34 cards)
What is a database?
A database is a shared, integrated computer structure that stores a collection of end-user data and metadata.
Name some advantages of the DBMS over file systems.
- Improved data sharing
- Improved data security
- Better data integration
- Minimized data inconsistency
What are some key problems with using spreadsheets as substitutes for databases?
- Complex system administration
- Lack of security and limited data sharing
- Extensive programming required
What were the key problems with file system data processing?
- Structural and data dependence
- Data redundancy
- Data anomalies
Why is data redundancy undesirable?
It leads to:
- Poor data security
- Data inconsistency
- Data-entry errors
- Data-integrity problems
What components make up a database system?
Hardware, software, people, procedures, and data
What are some disadvantages of database systems?
- Increased costs
- Management complexity
- Maintaining currency
- Vendor dependence
What components does a data model need to be “implementation ready”?
- A description of data structures that will store end-user data.
- Set of enforceable rules to guarantee data integrity.
- Data manipulation methodology to support real-world transformations.
What are the basic building blocks of every data model?
- Entities
- Attributes
- Relationships
- Constraints
What is the main difference between the network and the hierarchical data models?
The network model allows a given record to have more than one parent.
What was the key shortcoming of the network model?
It lacked ad hoc query abilities and required a large amount of coding even for simple reports.
From the end-user perspective, what three parts does any SQL-based relational database consist of?
- End-user interface
- Tables stored in the database
- SQL engine
What describes the main difference between the purposes of an object-oriented data model and a relational database model?
The object-oriented data model was created to address very specific engineering needs, while the relational database model was created for data management with a sound mathematical foundation.
What are the main reasons the relational database approach does not always satisfy the needs of organizations dealing with Big Data?
- The relational database is not designed for handling large amounts of unstructured data.
- Adding large amounts of data daily is costly in the relational environment.
- Data analysis with OLAP tools is not effective for unstructured data.
What are the four levels of abstraction shown by data models?
- Internal models
- External models
- Conceptual models
- Physical models
What does “logical independence” mean in the context of data models?
It means the internal model can be changed without affecting the conceptual model.
What are the three well-defined components of a relational model?
- A logical data structure represented by relations.
- A set of integrity rules.
- A set of operations for data manipulation.
What are the two requirements for entity integrity?
- All the values of the primary key must be unique.
2. No key attribute in the primary key can be null.
What is the requirement for referential integrity?
A foreign key may have either a null entry or an entry that matches the primary key value in a related table.
What two conditions define a weak entity?
- Entity is existence-dependent
2. Entity has a primary key that is partially or totally derived from parent entity.
What are the three, sometimes conflicting goals in designing databases?
- Adherence to design standards
- Processing speed
- Information requirements
What is the main goal of normalization?
Eliminate data anomalies by removing unnecessary data redundancies.
When is a table in Boyce-Codd Normal Form?
When every determinant in the table is a candidate key.
What are the five phases of the systems development life cycle?
- Planning
- Analysis
- Detailed systems design
- Implementation
- Maintenance
