DBMS Questions and Answers | 2023/2024

DBMS - Final
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1. What is SQL?: Structured Query Language. Includes statements for data defi-
nition, queries, and updates (Both DDL, and DML), Core specification, as well as
specialized extensions
2. What is Data Definition Language (DDL)?: A sublanguage that deals with the
creation, alteration, or deletion of a tables structure with CREATE, ALTER, and
DROP
3. What is the CREATE statement used for?: The main SQL command for data
definition that specifies a new relation (providing a name and spefifying attributes
and initial constraints) and can optionally specify schema
4. What is the ALTER statement used for?: The statement used to change a
schema in some form
5. What is the DROP statement used for?: The statement is used to remove
schema
6. A ____________ is a collection of ___________ which is a collection of
tables: Database; schemas
7. What is Data Manipulation Language (DML)?: The language element that al-
lows you to manipulate data in any SQL Server tables with commands like SELECT,
UPDATE, DELETE, and INSERT.
8. What is the SELECT statement used for?: It is the statement used for retrieving
information from a database. Follows the SELECT FROM WHERE form.
9. What can be used in the WHERE clause?: Comparison operators =, <, >, <=,
>=, <>

Like

% - replaces zero or more characters

_ - replaces a single character

Arithmetic Operations +, -, *, /

BETWEEN operation
10. What is the ORDER BY clause used for?: Used to order the output of the
select statement by using the keywords DESC or ASC to see result in descending
or ascending order
11. What is the UPDATE statement used for?: Modifies attribute values of one
or more selected tuples. Additional SET clause in the UPDATE command specifies
attributes to be modified and new values

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, DBMS - Final
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12. What is the DELETE statement used for?: Removes tuples from a relation.
Includes a WHERE clause to select the tuples to be deleted
13. What is the INSERT statement used for?: Inserts into a relation by specifying
the relation name and list of values for the tuple.
14. What can NULL mean?: Unknown value

Unavailable or withheld value

Not applicable attribute
15. How do you test for NULL in SQL?: You use <attribute> is NULL
not <attribute> = NULL
16. What are the characteristics of a correlated nested query?: Evaluated once
for each tuple in the outer query and contains a reference to the outer query
17. What are the characteristics of an uncorrelated nested query?: Evaluated
independently of the outer query and does not contain a reference to the outer query
18. What does the IN operator allow you to do in a WHERE clause?: Allows you
to specify multiple values in a WHERE clause, basically shorthand for multiple OR
conditions
19. What does the EXIST function do?: Checks whether the result of a correlated
nested query is empty or not

20. What does the UNIQUE(Q) function do?: Returns TRUE if there are no dupli-
cate tuples in the result of query Q
21. What does an INNER JOIN do?: It is the default type of join in a joined table
where a tuple is included in the result only if a matching tuple exists in the other
relation
22. What doe a LEFT OUTER JOIN do?: Every tuple in left table must appear
in result. If there are no matching tuples then it is padded with NULL values for
attributes of right table
23. What does a RIGHT OUTER JOIN do?: Every tuple in right table must appear
in result. If there are no matching tuples then it is padded with NULL values for
attributes of left table
24. What does a FULL OUTER JOIN do?: Every tuple from left and right that can
be joined will be in result. Unmatched tuples from left and right appear in the result
25. What are Aggregate Functions used for in SQL?: Used to summarize infor-
mation from multiple tuples into a single-tuple summary with functions like COUNT,
SUM, MAX, MIN, and AVG

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