Data Bases Flashcards
What is a Relational Database?
A database which recognises the
difference between entities and uses
different tables for each entity.
What is an entity?
An item of interest about which
information is stored.
What is a flat file?
A database that consists of a single file,
usually about one entity.
What is a primary key?
A unique identifier for each record in a
table.
What is a foreign key?
The attribute which links two tables
together.
What is a secondary key?
An index other than the primary key used
to search and sort through the database
with more convenience and speed.
What is normalisation?
This is the process of coming up with the
best layout for a relational database.
What does normalisation try to accomplish?
● No redundancy (unnecessary duplicates)
● Consistent data throughout linked tables.
● Records can be added and removed without issues.
● Complex queries can be carried out.
What is an index?
An index is a data structure used to look
up and access data in the database quickly.
What does capturing data mean?
Capturing data is the process of getting
the information you wish to use.
Is the primary key automatically indexed?
Yes
What method do banks use to capture data from
cheques?
They use Magnetic Ink Character
Recognition (MICR) to get all the details
apart from the amount which must be
entered manually
What does selecting data mean?
Selecting data is the process of reducing
excess information to obtain only the
data you require.
What does managing the data mean?
Managing the data means to manipulate
the information in any type of way such
as through sorting through it or selecting
certain parts using SQL.
What are the requirements to be in second normal
form?
- The database is in first normal form,
- There are no partial dependencies (no
composite keys)
What is the most common language used to
manipulate data in databases
SQL
What are the requirements to be in first normal form?
To be in first normal form there must be
no attribute that contains more than a
single value in a cell.
What are the requirements to be in the third normal
form?
- The database is in second normal
form. - There are no non-key dependencies
What does SQL stand for?
Structured Query Language
What is SQL?
A declarative language used to
manipulate databases.
What is referential integrity?
Referential integrity is the process of
ensuring consistency as it makes sure
that information is not removed if it is
required elsewhere in a linked database.
What is a transaction defined as?
A transaction is a single operation
executed on data.
What does ACID stand for?
Atomicity, Consistency, Isolation,
Durability
What does Atomicity (in ACID) mean?
A transaction must be processed in its
entirety or not at all.
What does consistency (in ACID) mean?
A transaction must maintain referential
integrity rules between linked tables.
What does isolation (in ACID) mean?
Simultaneous execution of transactions
should lead to the same result as if they
were executed one after the other.
What does durability (in ACID) mean?
Once a transaction has been executed it
will remain so regardless of the
circumstances
What is record locking?
Record locking is the process of
preventing simultaneous access to a
record.
What is the name of an issue that can arise as a result of record locking?
Deadlock
What is redundancy?
The process of creating more than one
copy of data in a physically different
location.
