Chaper 5- Databases Flashcards
Explain the term ‘validation’
Validation is the process of checking days when it is input. Validation is carried out buy a software, not by humans. It checks that data conforms to certain rules
What is meant by a range check?
This makes sure that the data falls between certain limits for example a date of birth for a student
What is meant by a length check?
This means the data must have a certain amount of characters or be above or below a limit. For example, most passwords must have over 8 characters so that they’re strong
Explain the term ‘verification’
This is checking that the data entered is correct
What is a check digit
This means data entered must be exactly the same as data previously entered. An algorithm calculates an extra digit which is appended to the data. The same algorithm checks the data when input
What validation is needed for a surname?
Type check
What validation is needed for a date of birth?
Range check
What validation is needed for gender?
Format check
Define the term data redundancy
Data redundancy is the unnecessary repetition of data
Explain what a DBMS is
A DBMS is a database management system. This allows multiple users to access a database without editing it in a way that would affect anyone else’s view of it. Its purpose is to protect data and run queries to extract data. Most DBMSs use data locking, this means that if one user has opened a record or tried to edit it, other users can’t view it until the transaction is carried out
What is a flat file database?
A flat file database consists of only one entity
Explain what a relational database is
Relational databases store their data into separate tables. The tables are linked together so that related days can be easily extracted
Describe four features of a typical DBMS
- Referential integrity
- Validation
- Security features
- Automatic backup
What is referential integrity
This means that changes must not be made that are logically impossible. For example, you cannot delete a student if there is a linked record to an exam entry. A DBMS will prevent this
What security features are available in a DBMS
- Groups can be created
- Read or write privileges can be assigned to different tables for different groups
