Databases Flashcards
1
Q
What are the advantages of a relational database?
A
- Reduces data duplication/redundancy
- Improves data consistency
- Easier to change data
- Easier to add data
- Improves data integrity
- Controls access to data
2
Q
State reasons why views of data are used.
A
- so users can access the data they need
- users do not need specialist knowledge
- to protect data
- to prevent unauthorised access
3
Q
State an applications of a flat file database and give a reason why.
A
Any simple data structure
- List of names and addresses for personal use only
- easy to maintain
4
Q
Explain what is meant by a secondary key.
A
- Allows the table to be sorted
- Allows the table to be searched
- Gives another way different to the primary key
5
Q
Describe a database management system.
A
- Software that…
- handles the complexities of managing a database
- may provide a user interface
- may use SQL to communicate with other programs
- provides different views of the data for different users
6
Q
State tasks that the DMBS performs.
A
- finds data
- adds new data
- updates data
- maintains indexes
- enforces data integrity rules
- manages access rights
7
Q
State the meaning of primary key.
A
unique identifier (in a table)
8
Q
What is DDL?
A
Data description language
9
Q
What is DML?
A
Data manipulation language
10
Q
What does DDL do?
A
- create new tables
- define foreign keys
- used for writing schema
11
Q
What does DML do?
A
- query data
- sort data into order
- update the data
12
Q
Explain the term report.
A
- presentation of selected data…
- …usually in the form of a table/specific layout
- may be defined in advance…
- …so the user does not need to set it up
13
Q
State two features of a report.
A
- a query
- a display order
14
Q
Explain the term data dictionary.
A
- A file containing descriptions of data in database…
- …stored in tables/as a relational database
- Uses metadata
- Used by database managers
- Used when altering database structure.
