Database administrators (DBAs) manage databases and are responsible for tasks like creating the database schema, defining storage structures and access methods, modifying the schema or physical organization when needed, granting authorization for data access, and specifying integrity constraints. Other database roles include application programmers, sophisticated users, specialized users, standalone users, native users, and system analysts who are responsible for database design, structure, and properties.

2. 1Q. What do you mean by DB? Discuss some applications of it.
Ans: A database is a collection of information that is organized so that it
can be easily accessed, managed and updated. Computer databases
typically contain aggregations of data records or files, containing
information about sales transactions or interactions with specific
customers.
Applications-

3. Q. Describe different levels of database user.
Ans. Database users are the one who really use and take the benefits of database.
1. Application Programmers
2. Sophisticated Users
3. Specialized Users
4. Stand-alone Users
5. Native Users
• Database Administrators - DBA can be a single person or it can be a group of
person. Database Administrator is responsible for everything that is related to
database. He makes the policies, strategies and provides technical supports.
System Analyst - System analyst is responsible for the design, structure and
properties of database. All the requirements of the end users are handled by
system analyst. Feasibility, economic and technical aspects of DBMS is the main
concern of system analyst.

4. Q. Describe the function of DBA.
Database Administrator: One of the main reasons behind using
DBMS is to have central control on both data and the applications
access those data. The person who has such central control over the
data is called a database administrator (DBA). Some of the functions of
DBA are given below-
• Five main functions of a database administrator are:
• ·To create the scheme definition
• ·To define the storage structure and access methods
• ·To modify the scheme and/or physical organization when necessary
• ·To grant authorization for data access
• ·To specify integrity constraints

5. 2Q. Explain database instance and schema
Definition of instance: The data stored in database at a particular moment of time is called instance
of database. For example: In the following diagram, we have a schema that shows the relationship
between three tables: Course, Student and Section. The diagram only shows the design of the
database, it doesn’t show the data present in those tables. Schema is only a structural view(design)
of a database as shown in the diagram below.
Database schema defines the variable declarations in tables that belong to a particular database;
the value of these variables at a moment of time is called the instance of that database.
For example, lets say we have a single table student in the database, today the table has 100
records, so today the instance of the database has 100 records. Lets say we are going to add
another 100 records in this table by tomorrow so the instance of database tomorrow will have 200
records in table. In short, at a particular moment the data stored in database is called the instance,
that changes over time when we add or delete data from the database.

6. Q. Define entity set and relationship set.
Ans. An entity set is a set of entities of the same type (e.g., all persons having an account
at a bank). Entity sets need not be disjoint. For example, the entity set employee (all
employees of a bank) and the entity set customer (all customers of the bank) may have
members in common.
Types of Entity Sets-
• Strong entity set
• Weak entity set
A relationship set is a set of relationships of the same type. ... For example, consider the
two entity sets customer and account. (Fig. 2.1 in the text). We define the relationship
CustAcct to denote the association between customers and their accounts.
Types of Relationship Sets-
• Unary relationship set
• Binary relationship set
• Ternary relationship set
• N-ary relationship se

7. Q. Describe database languages
Database Language
• A DBMS has appropriate languages and interfaces to express database queries and updates.
• Database languages can be used to read, store and update the data in the database.
1. Data Definition Language
• DDL stands for Data Definition Language. It is used to define database structure or pattern.
• It is used to create schema, tables, indexes, constraints, etc. in the database.
• Using the DDL statements, you can create the skeleton of the database.
• Data definition language is used to store the information of metadata like the number of tables and
schemas, their names, indexes, columns in each table, constraints, etc
2. DML stands for Data Manipulation Language. It is used for accessing and manipulating data in a database. It
handles user requests.
3. Data Control Language
• DCL stands for Data Control Language. It is used to retrieve the stored or saved data.
• The DCL execution is transactional. It also has rollback parameters.
4. Transaction Control Language
• TCL is used to run the changes made by the DML statement. TCL can be grouped into a logical transaction.

8. 3Q. Define super key and candidate key
Super Key: Super Key is an attribute (or set of attributes) that is used to uniquely identifies all
attributes in a relation. All super keys can’t be candidate keys but its reverse is true. In a relation,
number of super keys are more than number of candidate keys.
Candidate Key: Candidate key is a set of attributes (or attribute) which uniquely identify the tuples
in a relation or table. As we know that Primary key is a minimal super key, so there is one and only
one primary key in any relation but there is more than one candidate key can take place. Candidate
key’s attributes can contain NULL value which oppose to the primary key.

9. Q. Explain mapping cardinality for binary relationship
• Mapping cardinalities, or cardinality ratios, express the number of entities to which
another entity can be associated via a relationship set.
• Mapping cardinalities are most useful in describing binary relationship sets, although
they can contribute to the description of relationship sets that involve more than two
entity sets.
• For a binary relationship set R between entity sets A and B, the mapping cardinality must
be
• One-to-one. An entity in A is associated with at most one entity in B, and an entity in B
is associated with at most one entity in A
• One-to-many. An entity in A is associated with any number (zero or more) of entities in
B. An entity in B, however, can be associated with at most one entity in A
• Many-to-one. An entity in A is associated with at most one entity in B. An entity in B,
however, can be associated with any number (zero or more) of entities in A.
• Many-to-many.An entity in A is associated with any number (zero or more) of entities in
B, and an entity in B is associated with any number (zero or more) of entities in A.

10. Q. What do you mean by strong entity set & weak entity set? Explain with example.
• Strong Entity: Strong entity is not dependent of any other entity in schema.
Strong entity always has primary key. Strong entity is represented by single
rectangle. Two strong entity’s relationship is represented by single
diamond.
Various strong entities together makes the strong entity set.
• Weak Entity: Weak entity is depend on strong entity to ensure the
existance of weak entity. Like strong entity weak entity does not have any
primary key, It has partial discriminator key. Weak entity is represented by
double rectangle.
The relation between one strong and one weak entity is represented by
double diamond.

11. 4Q. What is quarry language? Classify them.
• Definition : Query language (QL) refers to any computer programming language that requests and
retrieves data from database and information systems by sending queries. It works on user entered
structured and formal programming command based queries to find and extract data from host
databases.
Query language may also be termed database query language.
Query language is primarily created for creating, accessing and modifying data in and out from a
database management system (DBMS). Typically, QL requires users to input a structured command that
is similar and close to the English language querying construct.
• For example, the SQL query: SELECT * FROM
Classify
• Thematic query:
Selection of all objects which achieve the required conditions (attributes). E.g.: "Select all spruce
trees."
• Geometric query:
Selection of all objects which achieve the required spatial conditions. E.g.: "Select all the houses that
are located less than 250 m away from the river".
• Topological query:
Selection of all objects which achieve the required conditions regarding the spatial relations between
the objects. For example: "Select all the buildings that are lying in zone 1".

12. Q. Explain fundamental operations of relational algebra
Relational algebra is a widely used procedural query language. It collects instances of
relations as input and gives occurrences of relations as output. It uses various operation to
perform this action.
Relational algebra operations are performed recursively on a relation. The output of these
operations is a new relation, which might be formed from one or more input relations.
Basic Relational Algebra Operations:
1. Unary Relational Operations
2. Relational Algebra Operations From Set Theory
3. Binary Relational Operations
4. SELECT (σ)
5. Projection(π)
6. Union operation (υ)
7. Intersection
8. Cartesian product(X)
9. Join Operations

13. Q. Explain Cartesian product operations of relational algebra
The Cartesian Product is also an operator which works on two sets. It is
sometimes called the CROSS PRODUCT or CROSS JOIN. It combines the
tuples of one relation with all the tuples of the other relation.

14. 5Q. Describe different part of SQL language.
SQL consists of three components:
• Data Definition Language (DDL)
• Data Manipulation Language (DML)
• Data Control Language (DCL)
The Data Definition Language (DDL). This component of the SQL language is used to create and
modify tables and other objects in the database. For tables there are three main commands:
• CREATE TABLE tablename to create a table in the database
DROP TABLE tablename to remove a table from the database
ALTER TABLE tablename to add or remove columns from a table in the database
The Data Manipulation Language (DML) component of the SQL language is used to manipulate
data within a table. There are four main commands:
• SELECT to select rows of data from a table
INSERT to insert rows of data into a table
UPDATE to change rows of data in a table
DELETE to remove rows of data from a table
The Data Control Language (DCL) This component of the SQL language is used to create
privileges to allow users access to, and manipulation of, the database. There are two main commands:
• GRANT to grant a privilege to a user
REVOKE to revoke (remove) a privilege from a user

15. Q. Explain the basic structure of SQL.
A relational database is a collection of tables. Each table has its own unique name.
The basic structure of an SQL expression consists of three clauses:
• The select clause which corresponds to the projection operation. It is
the list of attributes that will appear in the resulting table.
• The from clause which corresponds to the Cartesian-product
operation. It is the list of tables that will be joined in the resulting
table.
• The where clause which corresponds to the selection operation. It is
the expression that controls the which rows appear in the resulting
table.
Example : select dept_name
from instructor;
where dept_name = ’Comp. Sci.’ and salary > 70000;

16. Q. How can insert & delete data from a table with SQL? Explain with example.
Insert: The main goal of database systems is to store data in the tables. The data is usually supplied
by application programs that run on top of the database. Towards that end, SQL has the INSERT
command that is used to store data into a table. The INSERT command creates a new row in the
table to store data.
INSERT INTO `table_name`(column_1,column_2,...) VALUES (value_1,value_2,...);
Delete command : The basic syntax of the delete command is as shown below.
DELETE FROM `table_name` [WHERE condition];
HERE
•DELETE FROM `table_name` tells MySQL server to remove rows from the table ..
•[WHERE condition] is optional and is used to put a filter that restricts the number of rows
affected by the DELETE query.
If the WHERE clause is not used in the DELETE query, then all the rows in a given table will
be deleted. Before we go into more details discussion the DELETE command, let's insert
some sample data into the movies table to work with.

17. 6Q. What is domain constraints?
Q. What is foreign key? Explain basic concept of it.
Domain constraints can be defined as the definition of a valid set of values
for an attribute. The data type of domain includes string, character, integer,
time, date, currency, etc. The value of the attribute must be available in the
corresponding domain.
A foreign key is a column or group of columns in a relational database table
that provides a link between data in two tables. The concept of referential
integrity is derived from foreign key theory. Foreign keys and their
implementation are more complex than primary keys.
A foreign key is a column or group of columns in a relational database table
that provides a link between data in two tables. It acts as a cross-reference
between tables because it references the primary key of another table,
thereby establishing a link between them.

18. Q. Define database trigger? Explain the trigger mechanism with
an example.
A database trigger is procedural code that is automatically executed in
response to certain events on a particular table or view in a database.
The trigger is mostly used for maintaining the integrity of the
information on the database.
A database trigger is special stored procedure that is run when specific
actions occur within a database. Most triggers are defined to run when
changes are made to a table's data. Triggers can be defined to run
instead of or after DML (Data Manipulation Language) actions such as
INSERT, UPDATE, and DELETE.
• Example –
Suppose, we are adding a tupple to the ‘Donors’ table that is some
person has donated blood. So, we can design a trigger that will
automatically add the value of donated blood to the ‘Blood_record’
table.

19. Continue
Types of Triggers –We can define 6 types of triggers for each table:
• AFTER INSERT activated after data is inserted into the table.
• AFTER UPDATE: activated after data in the table is modified.
• AFTER DELETE: activated after data is deleted/removed from the
table.
• BEFORE INSERT: activated before data is inserted into the table.
• BEFORE UPDATE: activated before data in the table is modified.
• BEFORE DELETE: activated before data is deleted/removed from the
table.

20. 7Q. Define transaction?
Q. Describe ACID properties.
A transaction is a single logical unit of work which accesses and possibly modifies
the contents of a database. Transactions access data using read and write
operations. In order to maintain consistency in a database, before and after the
transaction, certain properties are followed. These are called ACID properties.

21. Q. Explain different states of transaction deadlock & deadlock handling
procedure
Deadlock : Deadlock is a state of a database system having two or more transactions,
when each transaction is waiting for a data item that is being locked by some other
transaction. A deadlock can be indicated by a cycle in the wait-for-graph. This is a
directed graph in which the vertices denote transactions and the edges denote waits
for data items.
• Example:
•  For example, in the following wait-for-graph, transaction T1 is waiting for data item X
which is locked by T3. T3 is waiting for Y which is locked by T2 and T2 is waiting for Z which is
locked by T1. Hence, a waiting cycle is formed, and none of the transactions can proceed
executing.

22. Cont.
•DEADLOCK HANDLING
• When a deadlock occurs, different operating systems
respond to them in different non- standard manners.
• The Major approaches are as follows
1. IGNORING DEADLOCK
2. DETECTION

23. 8Q. Short note on (a) RAID level (b) Normalization (c) Sequential file organization
• RAID stands for redundant array of independent disks. The technology combines two or
more physical drives into a logical unit presented as a single hard drive to the operating
system. Mirroring is duplicating data to more than one disk. It can speed read times
because the system can read data from more than one disk.
• Normalization is a database design technique which organizes tables in a manner that
reduces redundancy and dependency of data.
It divides larger tables to smaller tables and links them using relationships.
Sequential file organization : A sequential file contains records organized by the
order in which they were entered. The order of the records is fixed.
Records in sequential files can be read or written only sequentially.
After you place a record into a sequential file, you cannot shorten, lengthen, or
delete the record. However, you can update (REWRITE) a record if the length does
not change. New records are added at the end of the file.
If the order in which you keep records in a file is not important, sequential
organization is a good choice whether there are many