Exam 1 Flashcards
(30 cards)
define data independence, two reasons it is critical for application development?
the separation of the physical and logical views of the data
- data can be presented to the applications in any way
- changing the physical view doesn’t break everything above the logical view
will data integrity increase or decrease in a database versus a file env. and why
Data Integrity is INCREASED because the data is all in one place and to change the data you have to go to the location where it is found and change it. Then when someone else wishes to change the same data they do the same thing and see your changes
will hardware costs increase or decrease in a database compared to a file env. why?
Hardware Costs INCREASE because organizing all of the information takes a lot of physical space.
define metadata
data about the data
define ad hoc query
an “on the fly” query
define binding
mapping the logical to the physical view of the data
define domain
the sit of valid data for an attribute
explain an entity instance in the E-R model
a specific occurence of an entity class
explain an degree in the E-R model
the number of entities in a relationship
explain an minimum cardinality in the E-R model
the minimum number of instances in a relationship
explain an id-dependent weak entity in the E-R model
an entity that relies on another entity for its ID and existence in the database
explain an supertype in the E-R model
a parent entity
define, as related to normalization, functional dependency
given a value A you can look up or calculate exactly one value of B
define, as related to normalization, candidate key
the set of attributes that could be used as the primary key
define, as related to normalization, transitive dependency
a->b and b->c then a->c
define, as related to normalization, multidetermination
give a value A you can look up or calculate one or more values of B
define, as related to normalization, multivalued dependency
a->->b and (a->->c or a->c), b and c are not related
define 1NF
all relations
define 2NF
1NF + all non-key attributes are dependent on all of the key
define 3NF
2NF + no transitive dependencies
define BCNF
3NF + every dterminate is a candidate key
4NF
BCNF + no multivalued dependencies
define DK/NF
all the constraints on the relatoin are a logical consequence of the definition of domains and keys
the essence of DK/NF
“one theme per relation”
