Database Multiple Choice Questions on “SQL Basics and SQL Data Definition”.
1. Which one of the following is used to define the structure of the relation, deleting relations and relating schemas?
a) DML(Data Manipulation Langauge)
b) DDL(Data Definition Langauge)
c) Query
d) Relational Schema
Answer: b
Clarification: Data Definition language is the language which performs all the operation in defining structure of relation.
2. Which one of the following provides the ability to query information from the database and to insert tuples into, delete tuples from, and modify tuples in the database?
a) DML(Data Manipulation Langauge)
b) DDL(Data Definition Langauge)
c) Query
d) Relational Schema
Answer: a
Clarification: DML performs the change in the values of the relation.
3.
CREATE TABLE employee (name VARCHAR, id INTEGER)
What type of statement is this?
a) DML
b) DDL
c) View
d) Integrity constraint
Answer: b
Clarification: Data Definition language is the language which performs all the operation in defining structure of relation.
4.
What type of statement is this?
a) DML
b) DDL
c) View
d) Integrity constraint
Answer: a
Clarification: Select operation just shows the required fields of the relation. So it forms a DML.
5. The basic data type char(n) is a _____ length character string and varchar(n) is _____ length character.
a) Fixed, equal
b) Equal, variable
c) Fixed, variable
d) Variable, equal
Answer: c
Clarification: Varchar changes its length accordingly whereas char has a specific length which has to be filled by either letters or spaces.
6. An attribute A of datatype varchar(20) has the value “Avi”. The attribute B of datatype char(20) has value ”Reed”. Here attribute A has ____ spaces and attribute B has ____ spaces.
a) 3, 20
b) 20, 4
c) 20, 20
d) 3, 4
Answer: a
Clarification: Varchar changes its length accordingly whereas char has a specific length which has to be filled by either letters or spaces.
7. To remove a relation from an SQL database, we use the ______ command.
a) Delete
b) Purge
c) Remove
d) Drop table
Answer: d
Clarification: Drop table deletes the whole structure of the relation .purge removes the table which cannot be obtained again.
8.
DELETE FROM r; //r - relation
This command performs which of the following action?
a) Remove relation
b) Clear relation entries
c) Delete fields
d) Delete rows
Answer: b
Clarification: Delete command removes the entries in the table.
9.
INSERT INTO instructor VALUES (10211, ’Smith’, ’Biology’, 66000);
What type of statement is this?
a) Query
b) DML
c) Relational
d) DDL
Answer: b
Clarification: The values are manipulated. So it is a DML.
10. Updates that violate __________ are disallowed.
a) Integrity constraints
b) Transaction control
c) Authorization
d) DDL constraints
Answer: a
Clarification: Integrity constraint has to be maintained in the entries of the relation.