Database Reference
In-Depth Information
APPENDIX C
Glossary
Abstraction brings flexibility to your data models by redefining and
combining some of the attributes, entities, and relationships within the
model into more generic terms. For example, we may abstract
Employ-
ee
and
Consumer
into the more generic concept of
Person
. A
Person
can play many
Roles
, two of which are
Employee
and
Consumer
.
abstraction
ACID stands for Atomic, Consistent, Isolated, and Durable. Atomic
means everything within a transaction succeeds or the entire transaction
is rolled back. Consistent means that the data accurately reflects any
changes up to a certain point in time. A transaction cannot leave the
database in an inconsistent state. Isolated means transactions cannot in-
terfere with each other. That is, transactions are independent. Durable
means completed transactions persist even when servers restart or there
are power failures.
ACID
An alternate key is a candidate key that, although unique, was not chosen
as the primary key but still can be used to find specific entity instances.
alternate key
architect
