Databases Flashcards
What does Referential Integrity mean?
Prevents you from deleting related records
What is a serial file?
Permanent storage of data
- Data is in the order at which it was entered
- No order to the data is maintained
What is a sequential file?
- Data stored in order of a key field
- The order is maintained when new records are added
What is an indexed sequential file?
Maintain an index to allow groups of records to be accessed quickly.
What is a database?
A database is a structured, persistent collection of data
What are the advantages of using a database?
- Makes processing more efficient
- Reduces storage requirements
- Avoid redundancy
- Allows different users to only see relevant data
What is a DBMS?
Software which manages the database
What features does a DBMS provide?
- A manipulation language to access and change the data
- Integrity to ensure efficiency and structure is not compromised
- Additional security
- An interface for other programs to access and use the data
- Programs/data independence
What are the components of a database?
- Tables that store data in rows and columns
- Queries to manipulate data
- Forms or user interface
- Reports
What is a flat file?
One table and all data is stored within it.
What are the disadvantages of a flat file?
- Inefficient as it is not easy to query
- Data is duplicated (redundancy) inefficient use of storage. Errors can occur between different records easily and integrity is compromised.
What is a relational database?
A relational database has more than one related table.
How do you get from a flat file to a relational database?
Normalisation
What must be true for a relational database?
- Each record must be unique, primary key is unique identifier for the record.
What is a foreign key?
A field in one table that uniquely identifiers a row of another table or the same table.
