This set of Database Multiple Choice Questions & Answers (MCQs) focuses on “Set Operations”.
1. The union operation is represented by
a) ∩
b) U
c) –
d) *
View Answer
Explanation: Union operator combines the relations.
2. The intersection operator is used to get the _____ tuples.
a) Different
b) Common
c) All
d) Repeating
View Answer
Explanation: Intersection operator ignores unique tuples and takes only common ones.
3. The union operation automatically __________ unlike the select clause.
a) Adds tuples
b) Eliminates unique tuples
c) Adds common tuples
d) Eliminates duplicate
View Answer
Explanation: None.
4. If we want to retain all duplicates, we must write ________ in place of union.
a) Union all
b) Union some
c) Intersect all
d) Intersect some
View Answer
Explanation: Union all will combine all the tuples including duplicates.
5.
(SELECT course id FROM SECTION WHERE semester = ’Fall’ AND YEAR= 2009) EXCEPT (SELECT course id FROM SECTION WHERE semester = ’Spring’ AND YEAR= 2010);
This query displays
a) Only tuples from second part
b) Only tuples from the first part which has the tuples from second part
c) Tuples from both the parts
d) Tuples from first part which do not have second part
View Answer
Explanation: Except keyword is used to ignore the values.
6. For like predicate which of the following is true.
i) % matches zero OF more characters. ii) _ matches exactly one CHARACTER.
a) i-only
b) ii-only
c) i & ii
d) None of the mentioned
View Answer
Explanation: The % wildcard matches zero or more characters, while the _ wildcard matches exactly one character. Together, they offer flexibility and precision in pattern matching within the like predicate.
7. The number of attributes in relation is called as its
a) Cardinality
b) Degree
c) Tuples
d) Entity
View Answer
Explanation: None.
8. _____ clause is an additional filter that is applied to the result.
a) Select
b) Group-by
c) Having
d) Order by
View Answer
Explanation: Having is used to provide additional aggregate filtration to the query.
9. _________ joins are SQL server default
a) Outer
b) Inner
c) Equi
d) None of the mentioned
View Answer
Explanation: It is optional to give the inner keyword with the join as it is default.
10. The _____________ is essentially used to search for patterns in target string.
a) Like Predicate
b) Null Predicate
c) In Predicate
d) Out Predicate
View Answer
Explanation: Like predicate matches the string in the given pattern.
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