CS 6400 Exam 2
QUESTIONS AND VERIFIED
CORRECT ANSWERS
GRADED A+ [LATEST] 100%
GUARANTEED PASS
Mandatory Overlap relation - CORRECT ANSWER-Every instance of ET is an instance of ET1, ET2,
or both. A in ET1 and ET2 are foreign keys to A in ET. ET is A,B. ET1 is A, C. ET2 is A, D
non-mandatory overlap relation - CORRECT ANSWER-A in ET1 and ET2 are foreign keys to A in
ET
non-mandatory/disjoint - CORRECT ANSWER-A in ET1 and ET2 are foreign keys to A in ET
union type - CORRECT ANSWER-ET is a subset of the union of ET1 and ET2. ET-ID in ET1 and ET2
are foreign keys to ET-ID in ET
closed algebra - CORRECT ANSWER-each time there is an operation, you get a rational number
back. this allows you to formulate high level models. You can use previous thoughts to form new
thoughts for high level models
Relational algebra operators - CORRECT ANSWER-union
intersection
set difference
Cartesian product
, projection
selection
natural join
outer join
theta-join
divideby
rename
projection - CORRECT ANSWER-eliminates columns from a result
selection - CORRECT ANSWER-eliminates rows from a result
rename - CORRECT ANSWER-allows you to manipulate names of attributes of relations so join
and set operators work in the way they're intended
simple expresion - CORRECT ANSWER-take attribute name and compare to a constant or
compare attribute name to another attribute name
composite expression - CORRECT ANSWER-use AND (conjunction)
use OR (dis junction)
(expression) - change order of evaluation
NOT = negation
Relations are: - CORRECT ANSWER-sets!
Union - CORRECT ANSWER-The two relations in a union, intersection, or set difference must be
type compatible, i.e. same number of attributes and pairwise same types
QUESTIONS AND VERIFIED
CORRECT ANSWERS
GRADED A+ [LATEST] 100%
GUARANTEED PASS
Mandatory Overlap relation - CORRECT ANSWER-Every instance of ET is an instance of ET1, ET2,
or both. A in ET1 and ET2 are foreign keys to A in ET. ET is A,B. ET1 is A, C. ET2 is A, D
non-mandatory overlap relation - CORRECT ANSWER-A in ET1 and ET2 are foreign keys to A in
ET
non-mandatory/disjoint - CORRECT ANSWER-A in ET1 and ET2 are foreign keys to A in ET
union type - CORRECT ANSWER-ET is a subset of the union of ET1 and ET2. ET-ID in ET1 and ET2
are foreign keys to ET-ID in ET
closed algebra - CORRECT ANSWER-each time there is an operation, you get a rational number
back. this allows you to formulate high level models. You can use previous thoughts to form new
thoughts for high level models
Relational algebra operators - CORRECT ANSWER-union
intersection
set difference
Cartesian product
, projection
selection
natural join
outer join
theta-join
divideby
rename
projection - CORRECT ANSWER-eliminates columns from a result
selection - CORRECT ANSWER-eliminates rows from a result
rename - CORRECT ANSWER-allows you to manipulate names of attributes of relations so join
and set operators work in the way they're intended
simple expresion - CORRECT ANSWER-take attribute name and compare to a constant or
compare attribute name to another attribute name
composite expression - CORRECT ANSWER-use AND (conjunction)
use OR (dis junction)
(expression) - change order of evaluation
NOT = negation
Relations are: - CORRECT ANSWER-sets!
Union - CORRECT ANSWER-The two relations in a union, intersection, or set difference must be
type compatible, i.e. same number of attributes and pairwise same types
