| State reasons as to why databases are normalised | Minimise data redundancy
Minimise the chance of errors being made |
| What does 1NF do to a set of unnormalised data? | Only single values are allowed at each intersectin of a row and colum in a table
There must be no repeating groups |
| What does 2NF do to a set of unnormalised data? | Eliminate partial key dependancies |
| What does 3NF do to a set of unnormalised data? | No transative dependences |
| For a database...
State what an attribue is | specific characteristics of an entity |
| For a database...
State what an primary key is | The primary key is a field which uniquely identifies each record |
| For a database...
State what a composite primary key is | contents of two or more fields from a table to create a unique value |
| For a database...
State what a foriegn key is | Primary key from another table which is what allows tables to be linked |
| What are the types of errors that can be made in an unnormalised database? | Insertion
Update
Deletion |
| What is an insertion anomaly? | Inability to add data to a database due to the absence of other data |
| Whats a update anomaly | Same information can be expressed on multiple occureneces, so updates to the relatoin may result in lgical inconsistancies |
| What is a deletion anomaly | Unintended loss of data due to deletion of other data |
| Descrube what functional dependancy is | If the value of the first attribute changes the value of the second |
| What is meant by transitive dependences | Indirect relation between values in the same table |
| Whats meant by the term elimating partial key dependencies | Each non key attribute must be fully dependent on the whole primary key and not a subset of it |
| State wat a record is in database | A grouping of related data |
| Explain the concept of a relational database | A collective set of multiple data sets organized by tables, records and columns |
| What is SQL | SQL is a language used with databases |
| Whats an assumption made about each normailsation level | It has been normalisaed up to its own normalization level |
