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DBI 202 Exam |Questions with 100% Correct Answers
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DBI 202 Exam |Questions with 100% Correct Answers
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DBI 202 Exam |Questions with 100%Correct Answers
Which of the following is NOT a standard aggregation operator? - ✔ ✔ GROUP
T intersect(R union S) = (T intersect R) union (T intersect S)The above law still hold for
bag relations? - ✔ ✔ False
Choose the correct statement: Aggregate functions perform a calculation on a set of values
and return a single value. Aggregate functions perform a calculation on a single value and
return a single value - ✔ ✔ Aggregate functions perform a calculation on a set of values and
return a single value
SELECT SUM(D) FROM S WHERE D < 8 AND D > 5:a 4 6, c 6 8, c 5 5, e 9 9, F 10 10,c 7 9 - ✔ ✔ 6
(1,2), (1,2), (2,3), (3,4), (3,4), (4,1), (4,1), (4,1), (4,2) : SELECT a1.x, a2.y, COUNT(*) FROM Arc
a1, Arc a2 WHERE a1.y = a2.x GROUP BY a1.x, a2.y; - ✔ ✔ (3,1,2)
A B : 10 x, 30 y, 50 z, 70t, B C D:x 40 60,z 60 80,z 50 50,z 70 90 - ✔ ✔ (30,y) (70,t)
does the Boolean expression x <= 4 OR NOT(y >= 2 AND z = 10)have the truth value FALSE?
- ✔ ✔ x = 5, y = 3, z = 10
SELECT 'Nancy' + NULL + 'Smith' - ✔ ✔ NULL
,Granularity: the size of the lock- Granularity: the type of the lock-Mode: the type of the lock-
Duration: the time in seconds that the DBMS waits for a lock to be released - ✔ ✔ (a) and (c) and
(d) are true
What is the difference between the WHERE and HAVING SQL clauses? - ✔ ✔ The WHERE SQL
clause condition(s) is applied to all rows in the result set before the HAVING clause is applied
(if present). The HAVING clause is used only with SELECT SQL statements and specifies a search
condition for an aggregate or a group
R is the parent of S.And the relationship between R and S is set to "ON DELETE CASCADE" - ✔
✔ We can delete a row from R although that row has children in S (and in this case, all the
children will be deleted too)
To create a DEFAULT constraint on the "City" column of the table PERSON which is already
created, use the following SQL - ✔ ✔ ALTER TABLE Person ALTER COLUMN City SET
DEFAULT 'SANDNES'
a)Entity integrity(b) Domain integrity(c) Referential integrity(d) Primary key integrity - ✔ ✔
(a) and (b) and (c) are true
A(an) _____ asserts that a value appearing in one relation must also appear in the primary-key
component(s) of another relation - ✔ ✔ Foreign key constraint
A/An _____ is a data structure that makes it efficient to find those tuples that have a fixed value
for an attribute - ✔ ✔ Index
An index is a data structure used to speed access to tuples of a relation,given values of one or
more attributes. The key for index can be any attribute or set of attributes, and need not be
the key of the relation - ✔ ✔ All of the others.
A database of _____ data model is a collection of nodes, each node is either a leaf or interior -
✔ ✔ semi-structured
,Select the well-formed XML - ✔ ✔ <? xml version = "1.0" ?> <MovieData>
<Movie title="StarWar"><Year>1997</Year></Movie></MovieData>
A _____ specifies which characters are "less than" which other characters - ✔ ✔ Collation
In _____ Data Model, the data and relations between them are organized in tables -
✔ ✔ Relational
Why the intersection operator is not called a primitive relational algebra operator? -
✔ ✔ Because the intersection operator can be expressed through the union operator and
the difference operator
In SQL , the command/statement that let you add an attribute to a relation schema is - ✔ ✔ Alter
Schema-altering commands are known as _________ commands. - ✔ ✔ Data Definition
Language
What is a functional de pendency? - ✔ ✔ A functional dependency (A->B) occurs when
the attribute A uniquely determines B
What is a key attribute in a relation? - ✔ ✔ A key attribute is an attribute that belongs to one
of the keys of the relation
All relations in 3NF are also in BCNF. For any relation schema, there is a dependency-preserving
decomposition into 3NF - ✔ ✔ For any relation schema, there is a dependency-preserving
decomposition into 3NF
BCNF condition guarantees the non existence of the anomalies. In BCNF condition, the left
side of every non trivial FD must be a super key. - ✔ ✔ All of the others.
, What is the goal of decomposition when designing a database? - ✔ ✔ The goal of
decomposition is to replace a relation by several relations that do not exhibit anomalies
(a)We should pick the right kind of elements(b) When an entity has no non-primary key
attribute, we should convert that entity to an attribute(c) Use weak entities when-ever
possible(d) Always make redundancies - ✔ ✔ (a) and (b) are correct
The binary relationship between classes in UML is called - ✔ ✔ Association
H(x,y) <- S(x, y) AND x > 2 AND y < 6. Relation S(x, y) has 3 tuples (2, 3), (3, 5), and (4, 6). - ✔ ✔
H has a tuple (3, 5)
Let t appear w times in the relation: X union (Y intersect Z). - ✔ ✔ w <= x+y
When we apply set operators (UNION, INTERSECT, EXCEPT) to two relations R and S,
which conditions on R and S must be satisfied? - ✔ ✔ All of the others
A tuple which fails to participate in a join is called: - ✔ ✔ dangling tuple
TRUE OR NULL) return: - ✔ ✔ TRUE
No two null values are equal. Two null values are equal - ✔ ✔ No two null values are equal
In PSM, the difference between a stored procedure and a function is that - ✔ ✔ A function
has the return statement.
A User-Defined Type (UDT) in SQL can be the type of a table. A UDT can be the type of
an attribute belonging to some table - ✔ ✔ All of the others
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