Chapter 1 Flashcards
What is a Database?
A very large, integrated collection of data
Models real-world scenarios including entities and relationships.
What is a DBMS?
A software package designed to store and manage databases.
What are the main differences between files and DBMS?
- Applications must stage large datasets
- Special code for different queries
- Must protect data from inconsistency due to multiple concurrent users
- Crash recovery
- Security and access control
Why use a DBMS?
- Data independence and efficient access
- Data integrity and security
- Uniform data administration
- Concurrent access
- Recovery from crashes
- Reduced application development time
Why study databases?
Shift from computation to information, increasing datasets in diversity and volume.
What is a data model?
A collection of concepts for describing data.
What is a schema?
A description of a particular collection of data, using the given data model.
What is the relational model of data?
The most widely used model today, based on the concept of relations (tables with rows and columns).
What defines a conceptual schema?
The logical structure of the data.
What is the physical schema?
Describes the files and indices used.
What is logical data independence?
Protection from changes in the logical structure of data.
What is physical data independence?
Protection from changes in the physical structure of data.
What are the basic operations of relational algebra?
- Selection (σ)
- Projection (π)
- Cross-product (×)
- Set-difference (−)
- Union (∪)
How to select all 18 years old students in SQL?
SELECT * FROM Students S WHERE S.age=18
What command is used to create a table in SQL?
CREATE TABLE
