A database is a collection of information that is organized. So that it can easily be accessed, managed, and
updated.

DBMS stands for Database Management System. It is a collection of programs that enables user to create
and maintain a database.

The database and DBMS software together is called as Database system.

I. Redundancy is controlled.

II. Providing multiple user interfaces.

III. Providing backup and recovery

IV. Unauthorized access is restricted.

V. Enforcing integrity constraints.

It is a process of analyzing the given relation schemas based on their Functional Dependencies (FDs) and
primary key to achieve the properties
(1).Minimizing redundancy, (2). Minimizing insertion, deletion and update anomalies.

A collection of conceptual tools for describing data, data relationships data semantics and constraints.

This data model is based on real world that consists of basic objects called entities and of relationship among
these objects. Entities are described in a database by a set of attributes.

This model is based on collection of objects. An object contains values stored in instance variables with in
the object. An object also contains bodies of code that operate on the object. These bodies of code are
called methods. Objects that contain same types of values and the same methods are grouped together into
classes.

An entity is a thing or object of importance about which data must be captured.

A data base schema is specifies by a set of definitions expressed by a special language called DDL.

This language that enable user to access or manipulate data as organized by appropriate data model.
Procedural DML or Low level: DML requires a user to specify what data are needed and how to get those
data. Non-Procedural DML or High level: DML requires a user to specify what data are needed without
specifying how to get those data

It translates DML statements in a query language into low-level instruction that the query evaluation engine
can understand.

It executes low-level instruction generated by compiler.

Functional Dependency is the starting point of normalization. Functional Dependency exists when a
relation between two attributes allows you to uniquely determine the corresponding attributes value.

The first normal form or 1NF is the first and the simplest type of normalization that can be implemented in
a database. The main aims of 1NF are to:

1. Eliminate duplicative columns from the same table.

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2. Create separate tables for each group of related data and identify each row with a unique column (the
primary key).

A functional dependency X Y is full functional dependency if removal of any attribute A from X means
that the dependency does not hold any more.

A relation schema R is in 2NF if it is in 1NF and every non-prime attribute A in R is fully functionally
dependent on primary key.

A relation is in third normal form if it is in Second Normal Form and there are no functional (transitive)
dependencies between two (or more) non-primary key attributes.

A table is in Boyce-Codd normal form (BCNF) if and only if it is in 3NF and every determinant is a

candidate key.

Fourth normal form requires that a table be BCNF and contain no multi-valued dependencies.

A table is in fifth normal form (5NF) or Project-Join Normal Form (PJNF) if it is in 4NF and it cannot
have a lossless decomposition into any number of smaller tables.

A query with respect to DBMS relates to user commands that are used to interact with a data base.

The phase that identifies an efficient execution plan for evaluating a query that has the least estimated cost
is referred to as query optimization.

DBMS provides a systematic and organized way of storing, managing and retrieving from collection of
logically related information. RDBMS also provides what DBMS provides but above that it provides
relationship integrity.

SQL stands for Structured Query Language. SQL is an ANSI (American National Standards Institute)
standard computer language for accessing and manipulating database systems. SQL statements are used to
retrieve and update data in a database.

A stored procedure is a named group of SQL statements that have been previously created and stored in
the server database.

A view may be a subset of the database or it may contain virtual data that is derived from the database files
but is not explicitly stored.

A trigger is a SQL procedure that initiates an action when an event (INSERT, DELETE or UPDATE) occurs.

An index is a physical structure containing pointers to the data.

Extension -It is the number of tuples present in a table at any instance. This is time dependent.

Intension -It is a constant value that gives the name, structure of table and the constraints laid on it.

Atomicity-Atomicity states that database modifications must follow an?all or nothing? rule. Each
transaction is said to be ?atomic.? If one part of the transaction fails, the entire transaction fails.

Aggregation - A feature of the entity relationship model that allows a relationship set to participate in
another relationship set. This is indicated on an ER diagram by drawing a dashed box around the
aggregation.

Two important pieces of RDBMS architecture are the kernel, which is the software, and the data
dictionary, which consists of the system- level data structures used by the kernel to manage the database.

I/O, Security, Language Processing, Process Control, Storage Management, Logging and Recovery,
Distribution Control, Transaction Control, Memory Management, Lock Management.

You communicate with an RDBMS using Structured Query Language (SQL)

Data redundancy & inconsistency.

• Difficult in accessing data.
• Data isolation.
• Data integrity.
• Concurrent access is not possible.
• Security Problems.

It specifies user views and their mappings to the conceptual schema.

This language is to specify the internal schema. This language may Specify the mapping between two
schemas.

Concurrency control is the process managing simultaneous operations against a database so that database
integrity is no compromised. There are two approaches to concurrency control. The pessimistic approach
involves locking and the optimistic approach involves versioning.

A homogenous database is one that uses the same DBMS at each node. A heterogeneous database is one
that may have a different DBMS at each node.

A distributed database is a single logical database that is spread across more than one node or locations
that are all connected via some communication link.

Three-tier architecture includes a client and two server layers.

The application code is stored on the application server and the database is stored on the database server.
A two-tier architecture includes a client and one server layer. The database is stored on the database server.

Data definition language commands are used to create, alter, and drop tables. Data manipulation
commands are used to insert, modify, update, and query data in the database. Data control language
commands help the DBA to control the database.

Relations in a database have a unique name and no multivalued attributes exist. Each row is unique and
each attribute within a relation has a unique name. The sequence of both columns and rows is irrelevant.

An Internet database is accessible by everyone who has access to a Web site. An intranet database limits
access to only people within a given organization.

Deadlock is a unique situation in a multi user system that causes two or more users to wait indefinitely for
a locked resource.

A catalog is a table that contains the information such as structure of each file, the type and storage format
of each data item and various constraints on the data .The information stored in the catalog is called
Metadata.

Data warehousing and OLAP (online analytical processing) systems are the techniques used in many
companies to extract and analyze useful information from very large databases for decision making

Physical level: The lowest level of abstraction describes how data are stored.

Logical level: The next higher level of abstraction, describes what data are stored in database and what
relationship among those data.

View level: The highest level of abstraction describes only part of entire database.

Data independence means that the application is independent of the storage structure and access strategy of
data.

There are three major relationship models:-

One-to-one

One-to-many

Many-to-many

ORDER BY clause helps to sort the data in either ascending order to descending

DBCC stands for database consistency checker. We use these commands to check the consistency of the
databases, i.e., maintenance, validation task and status checks.

Collation refers to a set of rules that determine how data is sorted and compared.

Delete command removes the rows from a table based on the condition that we provide with a WHERE
clause. Truncate will actually remove all the rows from a table and there will be no data in the table after
we run the truncate command.

This is a primary file organization technique that provides very fast access to records on certain search
conditions.

A transaction is a logical unit of database processing that includes one or more database access operations.

Analysis phase

Redo phase

Undo phase

It is one, which keeps its physical structure hidden from user.

Addition, deletion and modification.

Structured data are facts concerning objects and events. The most important structured data are numeric,
character, and dates.

Structured data are stored in tabular form. Unstructured data are multimedia data such as documents,
photographs, maps, images, sound, and video clips. Unstructured data are most commonly found on Web
servers and Web-enabled databases.

Managing database structure, controlling concurrent processing, managing processing rights and
responsibilities, developing database security, providing for database recovery, managing the DBMS and
maintaining the data repository.

A dependency graph is a diagram that is used to portray the connections between database elements.

An exclusive lock prohibits other users from reading the locked resource; a shared lock allows other users
to read the locked resource, but they cannot update it.

SQL statements return a set of rows, while an application program works on one row at a time. To resolve
this mismatch the results of SQL statements are processed as pseudofiles, using a cursor or pointer to
specify which row is being processed.

(1)Providing default values, (2) enforcing data constraints,

(3) Updating views and (4) enforcing referential integrity

The advantages of stored procedures are (1) greater security, (2) decreased network traffic, (3) the fact that
SQL can be optimized and (4) code sharing which leads to less work, standardized processing, and
specialization among developers.

Entities have attributes. Attributes are properties that describe the entity's characteristics. Entity instances
have identifiers. Identifiers are attributes that name, or identify, entity instances.

Enterprise Resource Planning (ERP) is an information system used in manufacturing companies and
includes sales, inventory, production planning, purchasing and other business functions. An ERP system
typically uses a multiuser database.

Embedded SQL is the process of including hard coded SQL statements. These statements do not change
unless the source code is modified. Dynamic SQL is the process of generating SQL on the fly. The
statements generated do not have to be the same each time.

A join allows tables to be linked to other tables when a relationship between the tables exists. The
relationships are established by using a common column in the tables and often uses the primary/foreign
key relationship.

A subquery is a query that is composed of two queries. The first query (inner query) is within the WHERE
clause of the other query (outer query).

The hierarchical model is a top-down structure where each parent may have many children but each child
can have only one parent. This model supports one-to-one and one-to-many relationships.

The network model can be much more flexible than the hierarchical model since each parent can have
multiple children but each child can also have multiple parents. This model supports one-to-one,
one-to-many, and many-to-many relationships.

A dynamic view may be created every time that a specific view is requested by a user. A materialized view
is created and or updated infrequently and it must be synchronized with its associated base table(s).