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level: Database design and normalisation techniques

Questions and Answers List

level questions: Database design and normalisation techniques

QuestionAnswer
State reasons as to why databases are normalisedMinimise 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 isspecific characteristics of an entity
For a database... State what an primary key isThe primary key is a field which uniquely identifies each record
For a database... State what a composite primary key iscontents of two or more fields from a table to create a unique value
For a database... State what a foriegn key isPrimary 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 anomalySame information can be expressed on multiple occureneces, so updates to the relatoin may result in lgical inconsistancies
What is a deletion anomalyUnintended loss of data due to deletion of other data
Descrube what functional dependancy isIf the value of the first attribute changes the value of the second
What is meant by transitive dependencesIndirect relation between values in the same table
Whats meant by the term elimating partial key dependenciesEach non key attribute must be fully dependent on the whole primary key and not a subset of it
State wat a record is in databaseA grouping of related data
Explain the concept of a relational databaseA collective set of multiple data sets organized by tables, records and columns
What is SQLSQL is a language used with databases
Whats an assumption made about each normailsation levelIt has been normalisaed up to its own normalization level