1.3.2 Flashcards
what are the problems with adding a second entry of the same customer on a flat file
only one customer entry is allowed so would not be able to add a second entry
customer data would be repeated resulting in wasted space
how can we ensure that the database is in 1NF
data is atomic
no repeating fields
has a primary key
how can a database be considered to be in 2NF
it has to be in 1NF
every field is dependent on the primary key
how can a database be considered to be in 3NF
it has to be in 2NF
transitive relationship
what is meant by the term hash
when a value is entered into an algorithm and it is converted into another value
what is a primary key
A field which uniquely identifies a record
what is a transaction
a single operation executed on data
what is redundancy
when a copy of data is created in more than one physical location
what are the advantages of hash
the process cannot be reversed, so the initial value cannot be discovered
what is referential integrity
ensures that information is not removed if it is required anywhere else in the linked table
ensures that data is accurate and consistent within a relationship
what is a relational database
uses different tables for different entities
what is record locking
prevents simultaneous access of records in a database
what does Atomicity mean
a transaction is either processed completely or not at all
what does Consistency mean
A transaction must maintain referential integrity rules
what does Isolation mean
simultaneous executions of transactions must lead to the same result
