YEAR 1 CO1 WEEK 17 DATABASES Flashcards
Define a database.
A collection of related data stored in a logical and structured way.
State and describe the parts of a database.
Table/file : collection of related records which contain the same type of information as all the other records.
Record : all of data relating to one item or thing.
Field : stores one item of data in a record.
Define a Flatfile Database.
Usually stores only one table with no links between them.
State the disadvantages of a Flatfile Database.
And the one advantage.
May have redundant data (repeated).
Potential duplicated data.
Harder to update due to data duplication.
Records are not unique.
Security poor as once gained access all data is readily available.
Harder to perform more complex queries.
Easy to setup and understand.
Define a Relational Database.
Has more than one table which are linked together by primary and foreign keys.
State the advantages of Relational Database and the one disadvantage.
Data only stored once.
Data integrity is maintained.
Easy to modify the format.
Security is better as sections of data can be individually protected using authorisation.
More future proof.
Hard to set up.
Define a primary key.
Used to uniquely identify a record.
Define a foreign key.
A primary key in one table which is used as an attribute in another table to link between tables.
Define a secondary key.
They act as indexes for easier sorting and faster searching.
May not be unique
And for sorting and searching data.
Define data integrity.
Refers to the correctness of data over the lifetime of the data
State and explain the three types of data integrity.
Entity Integrity : every table must have a primary key which is unique and not empty.
Referential Integrity : foreign keys must point to a primary key of another table but can be empty.
Domain Integrity : all attributes in databases are related to the overall domain database that the database is working on.
Define data consistency.
When data is held in more than one field it should be stored in a consistent way.
Define data independence.
Refers to separation of data from program that uses it.
