DBI202 EXAM NEWEST 2024 ACTUAL
EXAM TEST BANK COMPLETE
QUESTIONS AND CORRECT ANSWERS
(VERIFIED ANSWERS) ALREADY
GRADED A+
What is the goal of decomposition when designing a database? - Answer-The goal of
decomposition is to replace a relation by several relations that do not exhibit anomalies
When drawing an ERD:(a)Entity sets and their attributes should reflect
reality(b)Redundancy is not important, so we can ignore it(c) Avoid introducing more
elements into the design than is absolutely necessary(d) Choosing the right
relationships - Answer-(a) and (c) and (d) are correct
Which of the followings is true? - Answer-All of the others
Choose the correct statement: - Answer-Aggregate functions perform a calculation on a
set of values and return a single value
Compute the union of the relation R(A,B,C): Which of the following tuples DOES NOT
appear in the result? - Answer-(1,5,4)
When join R and S, we want to display all the records in R we must use: - Answer-LEFT
OUTER JOIN
Choose one right answer - Answer-All of the others
A database transaction, by definition, must be ACID (atomic, consistent, isolated and
durable). What does �Consistent� mean? - Answer-�Consistent� means that:
Transactions must not violate any integrity constraints during its execution
What is the difference between the WHERE and HAVING SQL clauses? - Answer-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
Pay attention to the following query:SELECT * FROM R WHERE A LIKE �%_%�; So,
in the above case, the wildcard �_� represents what? - Answer-�_� represents
exactly 1 character
,A foreign key must - Answer-have either a matching value in the referring (primary)
table OR be NULL
Suppose we have 2 relations R(A,B,C,D) and S(B,C,D,E) and B is the foreign key
column in R and B is the primary key in S.This means that: when enter data into the
column B in R, only values that belong to ?B(S) are permitted - Answer-TRUE
In UML, a _____ between classes is called an association - Answer-binary relationship
Choose the correct statement - Answer-Except for COUNT, aggregate functions ignore
null values
Suppose the relation S(B,C,D) has tuples: Compute the result of the following query:
SELECT D, SUM(C)FROM S GROUP BY D - Answer-(9,16)
Column A of a relation has the following list of values in the six rows of the table: NULL,
NULL, 10, 10, 20, 30 In SQL Server, which of the following is the correct value of
AVG(DISTINCT A)? - Answer-20
What is the difference between Where and Having Clause? - Answer-WHERE is for
Rows and HAVING is for Groups
Suppose relation R(a,b,c) has the following tuples: Which tuple is contained in the result
of the following query: - Answer-Selects all customers from table Sales that have made
more than 5 orders.
The relation R(A,B) may have duplicate tuples. Choose the query that create non-
duplicated results, regardless of what tuples R contains? - Answer-SELECT A, B FROM
R GROUP BY A, B
The table R(X,Y) currently has the following tuples (note there are duplicates).The
relation S(A,B,C) has the following tuples: Which is the result when we execute the
following query: - Answer-There is an error
What is a "join"? - Answer-�join� used to connect two or more tables logically with or
without common field(s)
Given relations R(A,B) and S(B,C,D). The result of natural join of the relations R and S
has - Answer-Attributes A, B, C, D
(TRUE OR NULL) return: - Answer-TRUE
Relation R(x,y) currently consists of only one tuple (NULL, NULL). Which of the
following queries will produce a nonempty output? That is, at least one tuple will be
produced, although the tuple(s) may have NULL's. - Answer-SELECT * FROM R
WHERE x IS NULL
,(TRUE AND NULL) returns: - Answer-NULL
Choose one correct statement: - Answer-Comparisons between two null values, or
between a NULL and any other value, return unknown
A database transaction, by definition, must be ACID (atomic, consistent, isolated and
durable). What does �Durable� mean? - Answer-�Durable� means that:
Transactions that have committed will survive permanently
A database transaction, by definition, must be ACID (atomic, consistent, isolated and
durable). What does �Isolated� mean? - Answer-�Isolated� means that: how/when
the changes made by one operation in one transaction become visible to other
concurrent operations in other transactions
Choose the in-correct statement: - Answer-In SQL Server, every DML operation is a
transaction regardless of whether it has a BEGIN TRANSACTION or not
The above describes which property of a transaction? - Answer-Durability
Pay attention into the following query:SELECT * FROM R WHERE A LIKE
�%a%�;So, in the above case, the wildcard % represents what? - Answer-% (percent
sign) represents zero, one, or more characters
In relational data model, an attribute is a column - Answer-False *
A data model is a notation for describing data or information. And the description
generally consist of: - Answer-3 parts *
DBMS stands for what? - Answer-Database Management System *
Look at this line: MOVIES (Id, Name, Description) What the above represent? - Answer-
A schema *
Look at the following data for table R: .............. - Answer-R is a relation *
Choose all correct statements: - Answer-set of rows ,,Data Mode
Choose 3 important data models that we will study in database course - Answer-
Network ,Hierachical,Relational
In relational data model, a tuple is a record or a row - Answer-true
When the Relational Data Model first proposed? - Answer-1970
What is the oldest data model? - Answer-Network Data Model
, How many data models mentioned in our database course? - Answer-6
XML files are semi-structured data - Answer-true
A relation is a list of tuples - Answer-false
A relation is a set of tuples - Answer-true
What is the father of relational data model? - Answer-Adgar Codd
In relational data model, an attribute is a column - Answer-false
A data model is a notation for describing data or information. And the description
generally consist of: - Answer-3 parts
A weak entity: - Answer-both (a) and (b)
Give the relation R(XYZT) with the following FD's: XY -> Z ; XYT -> Z ; XYZ -> T ; XZ ->
T - Answer-R is not in BCNF
Given the relation schema R(XYZT) and functional dependencies F = {X->Z, T->Y}. -
Answer-both X->Z and T->Y
The highest normal form for relation schema R(XYZ) with functional dependencies: F =
{XY-> Z; Y->X; Z->Y } is: - Answer-3NF
Give the relation R(EFGH) with the following FD's: E -> F ; F -> E ; E -> H ; H -> F -
Answer-R is in 3NF
Give the relation R(ABCDE) with the following FD's: D -> C, CE-> A, D ->A, and AE ->D
- Answer-ABE
Which of the following relations is in Third normal form (3NF)? - Answer-ACD -> B ; AC
-> D ; D -> C ; AC -> B
Let R(ABCDEFGH) satisfies the following functional dependencies: A -> B, CH -> A, B -
> E, BD -> C, EG -> H, DE -> F. - Answer-ADG -> CH
Which of the following statements are correct? (choose 2) - Answer-bo? in 3NF are also
in BCNF
Which of the following relations is in Boyce-Codd Normal Form (BCNF)? - Answer-BD -
> C ; AB -> D ; AC -> B ; BD -> A
How many design principles are there in our course when drawing an ERD? - Answer-5
