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WGU C192 Data Management for Programmers With Complete Solutions 2024
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10/11/24, 8:34 AMWGU C192 Data Management for Programmers
Jeremiah
Terms in this set (151)
external schema Also called a subschema, this is a specific view of the data utilized by an end user
This describes all the entities, attributes, and relationships together with integrity
conceptual schema
constraints. Each DB has exactly one.
A complete description of the internal model, down to the physical storage of data.
internal schema
Each DB has exactly one.
logical data independence The immunity of the external schemas to changes in the conceptual schema
physical data independence The immunity of the conceptual schema to changes in the internal schema
An integrated collection of concepts for describing and manipulating data,
data model relationships between data, and constraints on the data in an organization
(structural, manipulative, constraints)
The process of constructing a detailed architecture for a database that is
conceptual modeling
independent of implementation details
The process of constructing a model of the data based on a specific data model, but
logical modeling
that is independent of implementation details
Term for the structure of a relation/table, together with a specification of the
intension
domains and any other restrictions on possible values
extension (state) Term for the tuples of a relation, which change over time
degree (relation) Term for the number of attributes a relation/table contains
cardinality (relation) Term for the number of tuples in a relation/table. Changes over time.
superkey An attribute, or set of attributes, that uniquely identifies a tuple within a relation
A superkey such that no proper subset is a superkey within the relation (atomic
candidate key
superkey)
alternate keys The candidate keys that are not selected to be the primary key
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If a foreign key exists in a relation, either the foreign key value must match a
referential integrity candidate key value of some tuple in its home relation or the foreign key value must
be wholly null
A named relation corresponding to an entity in the conceptual schema, whose
base relation
tuples are physically stored in the database
The dynamic result of one or more relational operations operating on the base
relations to produce another relation; a virtual relation that does not necessarily exist
view
in the database but can be produced upon request by a particular user, at the time
of request
The property allowing expressions to be nested in the relational algebra, just as we
closure
can nest arithmetic operations
Relational algebra operation that works on a single relation R and defines a relation
selection (restriction)
that contains only those tuples of R that satisfy the specified condition (predicate)
Relational algebra operation that works on a single relation R and defines a relation
projection that contains a vertical subset of R, extracting the values of specified attributes and
eliminating duplicates (i.e., selecting specific columns from a table)
Relational algebra operation that defines a relation that contains all the tuples of R,
union or S, or both R and S, duplicate tuples being eliminated. R and S must be union-
compatible.
Relational algebra operation that defines a relation consisting of the tuples that are in
difference
relation R, but not in S. R and S must be union-compatible.
Relational algebra operation that defines a relation consisting of the set of all tuples
intersection
that are in both R and S. R and S must be union-compatible.
Relational algebra operation that defines a relation that is the concatenation of every
Cartesian product
tuple of relation R with every tuple of relation S
Relational algebra operation that provides a new name S for the expression E, and
rename
optionally names the attributes as a1, a2, . . . , an. (Greek letter rho)
Relational algebra operation that defines a relation that contains tuples satisfying the
Theta join (θ) predicate F from the Cartesian product of R and S. The predicate F is of the form R.ai
θ S.bi, where θ may be one of the comparison operators (<, ≤, >, ≥, =, ≠).
Equijoin A Theta join where the predicate F contains only equality (=)
Relational algebra operation that is an Equijoin of the two relations R and S over all
Natural join common attributes x. One occurrence of each common attribute is eliminated from
the result.
Relational algebra operation that is a join in which tuples from R that do not have
Outer join matching values in the common attributes of S are also included in the result relation.
Missing values in the second relation are set to null.
Relational algebra operation that defines a relation that contains the tuples of R that
Semijoin
participate in the join of R with S satisfying the predicate F.
Relational algebra operation that defines a relation over the attributes C that consists
Division
of the set of tuples from R that match the combination of every tuple in S
ESCAPE SQL keyword used to define an escape character
True or false: When GROUP BY is used, each item in the SELECT list must be single-
True
valued per group
True or false: The WHERE clause filters individual rows going into the final result
True
table, whereas HAVING filters groups going into the final result table
WGU C192 Data Management for Programmers
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