Class XII Informatics Practices Paper (Chapter Wise With
ORACLE SQL REVISION TOUR AND
Q1. (a)Define the term candidate key and foreign key with respect to
database. (b) Define the term primary key and alternate key with respect to database.
Ans. (a) CANDIDATE KEY- All attribute combinations inside a relation that
can serve as a primary key are candidate keys as they are candidates for primary
FOREIGN KEY- A non-key attribute, whose values are derived from the primary key
of some other table, is known as foreign key in its current table.
(b)PRIMARY KEY- This refers to a set of one or more attributes that can uniquely
identify tuples within the relation.
ALTERNATE KEY- A candidate key, that is not primary key, is called an alternate
Q2. Differentiate between DDL and DML commands. Give one example of each type of
Ans: The Data Definition Language (DDL) commands, as the name suggests,
allow you to perform tasks related to data definition. That is, through these
commands, you can perform tasks alter and drop schema objects, grant and revoke
The Data Manipulation Language (DML) commands, as the name suggests, are used to
manipulate data. That is, DML commands query and manipulate data in existing
Q3. Name the keyword used to (i) assign a value as no data (ii) avoid duplicate
rows in SQL query.
Ans: (I) NULL (ii) UNIQUE
Q4. What is a view? Why does view not requires any physical storage?
Ans. A view is a virtual table that can be thought of as an SQL SELECT
statement that selects data from a single table or joined table(s), but can be
accessed as though it were a single table.
A view does not require physical storage because a view is a virtual table that
does not exist in reality, but is a logical definition of a set of relative
columns, usually from multiple tables.
Q5. Define SQL. Name the different SQL subcategories.
Ans: The Structure Query Language (SQL) is a language that enables you to
create and operate on relational databases. It is a standard relational database
language.SQL command is divided into following categories:
(i) Data Definition Language (DDL) Commands
(ii)Data Manipulation Language (DML) Commands
(iii) Transaction Control Language (TCL) Commands
(iv) Session Control Commands
(vi)System Control Commands