Database and Data Modelling Flashcards
What is a file-based system?
Data stored in separate files that can be accessed
What is one disadvantage of file-based systems?
No control over file organization or structure
Why is data redundancy a problem in file-based systems?
Data must be changed manually in every file where it appears
Why is a file-based system not suitable for multi-user environments?
It becomes chaotic and lacks coordination
How secure is a file-based system?
Security is not sophisticated; users can access everything
What is a database?
A collection of non-redundant interrelated data
What is a DBMS?
Software that defines
Where is data stored in a DBMS?
In relational databases (tables in secondary storage)
What does a data dictionary contain?
List of all files
What is data modeling in a DBMS?
Analyzing data objects and identifying relationships among them
What is a logical schema?
An overall view of the database including entities
What is data integrity in a DBMS?
Ensures data block is copied
How does a DBMS ensure data security?
By using passwords
What is record locking?
Preventing other users from editing a record currently being modified
What is deadlock in a DBMS?
When two users hold locks needed by the other
How can deadlocks be resolved?
DBMS detects and aborts one of the users’ tasks
What is a developer interface in a DBMS?
Interface to create/manipulate a database using SQL
What does a query processor do?
Parses
What is an entity in a relational database?
An object or event that can be identified distinctly
What is a table in a database?
A group of related entities stored in rows and columns
What is a tuple?
A row or record in a database table
What is an attribute?
A field or column in a database table
What is a primary key?
An attribute(s) that uniquely identifies a tuple
What is a candidate key?
An attribute that could serve as a primary key
