Database Managment System
Category : Banking
Database Management System
Database Management Systems (DBMS) are specially designed software which is used to create and maintain a database. It acts as an interface between users and a database or multiple databases. DBMS is comprised of tables that made up of rows called records and columns called fields.
The important processes catered by existing DBMS are as below:
SOME OF THE DATABASE MANAGEMENT SYSTEM ARE
(1) Microsoft Access: This is the database management system developed by Microsoft. It stores data in its own format based on the Access Jet Database Engine. It also has the facilities like importing or linking directly to data stored in other databases and applications.
(2) MySQL: MySQL is open source database management system, one of the most popular dbms on the web. It is reliable, fast and also flexible.
(3) Oracle: Developed by Oracle corporation. It is object relational database management system. The original version of Oracle software was developed by Software Development Laboratories (SDL). Oracle is regarded to be one of the safe DBMS.
(4) Microsoft SQL Server: Microsoft developed this relational database server. The primary function of this software is to store and retrieve the data as requested by other applications, whether those applications are on the same computer or running on other computers across the network (including internet).
COMPONENTS OF DATABASE SYSTEM
The database system can be divided into four components.
DATABASE TABULAR MODEL
Database in tabular form contain. Row and Column database.
In a database, a row also called a tuple represents a single row, implicitly structured data item in a table.
A database table can be thought of as consisting of rows and columns or fields. Each row in a table represent a set of related data, and every tuple in the table has the same structure.
Example: A table that represents companies, each row would represent a single company. Columns might represent things like company name, company street address, whether the company is publicly held, its TIN number, VET number, etc.
In a database, a column is a set of data values of a particular simple type, one for each row of the table. The columns provide the structure according to which the rows are composed.
In database terminology, column's equivalent is called attribute.
Example: A table that represents companies might have the following columns: ID (integer identifier, unique to each row). Name (text), Address line 1 (text), Address line 2 (text). Postal code (text), city (text), industry (text), etc.
Column (Field) 1
Column (Field) 2
(Record) Row 1
Row 1, Column 1
Row 1, Column 2
(Record) Row 2
Row 2, Column 1
Row 2, Column 2
(Record) Row 3
Row 3, Column 1
Row 3, Column 2
A Database model defines the logical design of data. The model describes the relationships between different parts of the data. In history of database design, three models have been in use.
(i) Hierarchical Model: In this model each entity has only one parent but can have several children. At the top of hierarchy there is only one entity which is called Root.
(ii) Network Model: In the network model, entities are organized in a graph, in which some entities can be accessed through several path.
(iii) Relational Model: In this model, data is organised in two-dimensional tables called relations. The tables or relation are related to each other.
Database design is the process of producing a detailed data model of database. This data model contains all the needed logical and physical design choices and physical storage parameters needed to generate a design in a data definations language, which can be used to create a database. A fully attributed data model contains detailed attributes of each entity.
ENTITY RELATIONSHIP MODEL
E-R model is a very popular conceptual data model which is used to develop conceptual design of databases
This data model describes or perceives the real world data in form of entities.
The E-R Model: The enterprise is viewed as set of
Symbols used in E-R Diagram
An ENTITY is a basic unit of E-R model which is an object or a thing in real world having independent existence. An entity may be concrete and a physical existence (e.g.: person, place) or it can be abstractor conceptual existence like loan, course. Entity is an object that is involved in the enterprise and that be distinguished from other objects.
ENTITY SET: It is a collection of entities of a particular entity type at any point of time. For example: A firm is having many employees, these are denned as entities (el, e2, e3, .en) and all these entities are having same attributes under entity type employee. The set of students (e 1, e2, e3......) is entity set.
TYPES OF ENTITY SET
Weak: An entity set that does not have a primary key is referred to as a Weak entity set. The existence of a weak entity set depends on the existence of a strong entity set; it must relate to the strong set via a one-to-many relationship set. The discriminator (or partial key) of a weak entity set is the set of attributes that distinguishes among all the entities of a weak entity set.
Example: We depict a weak entity set by double rectangles. We underline the discriminator of a weak entity set with a dashed line. Payment-number - discriminator of the payment entity set Primary key for payment - (loan-number, payment-number)
The table shows the difference between Strong Entity set and Weak Entity set
Strong Entity set
Week Entity set
It has its own primary key.
I does not save sufficient attributes to form a primary key on its own.
It is represented by a rectangle.
It is represented by a double rectangle.
It contains a primary key represented by an underline.
It contains a Partial Key or discriminator represented by a dashed underline.
The member of strong entity set is called as dominant entity set.
The member of weak entity set is called as subordinate entity set.
The Primary key is one of its attributes which uniquely identifies its member.
The Primary Key of weak entity set is a combination of partial key and primary key of the strong entity set.
The relationship between two strong entity set is represent by a diamond symbol.
The relationship between one strong and a weak entity set is represented by a double diamond sign. It is known as identifying relationship.
The line connecting strong entity set with the relationship is single.
The line connecting weak entity set with the identifying relationship is double.
To participation in the relationship may or may not exist.
Total participation in the identifying relationship always exists.
VALUE SET OR DOMAIN VALUES
A set of possible values that can be assigned to a given attribute in individual entity. For example, the attribute employee name in employee entity type can have character data and integer value. Hence the values in this attribute will be a non- integer domain.
It is the set of similar objects or a category of entities; they are well defined
It describes one aspect of an entity type; usually [and best when] single valued and indivisible (atomic)
It is the possible values of an attribute.
FUNCTIONS OF DBMS
ADVANTAGES OF DBMS
DISADVANTAGES OF DBMS
RDBMS (RELATIONAL DATABASE MANAGEMENT SYSTEM)
RDBMSs have become a predominant choice for the storage of information in new databases used for financial records, manufacturing and logistical information, personnel data, and much more since the 1980s. Relational databases have often replaced legacy hierarchical databases and network databases because they are easier to understand and use. However, relational databases have been challenged by object databases, which were introduced in an attempt to address the object-relational impedance mismatch in relational database, and XML databases.
Relational data model describes the world as "a collection of inter-related relations (or tables).
Relational databases are powerful because they require few assumptions about how data is related or how it will be extracted from the database. As a result, the same database can be viewed in many different ways. An important feature of relational systems is that a single database can be spread across several tables. This differs from flat-file databases, in which each database is self-contained in a single table.
Almost all full-scale database systems are RDBMS's. Small database systems, however, use other designs that provide less flexibility in posing queries.
An important constraint on the entities is the key. The key is an attribute or a group of attributes whose values can be used to uniquely identify an individual entity in an entity set. Types of keys are described below:
Employee (EID, First Name, Last Name, SIN, Address, Phone, Birth Date. Salary, Department ID) Possible candidate keys are EID, SIN
First Name and Last Name — assuming there is no one else in the company with the same name, Last Name and Department ID - assuming two people with the same last name don't work in the same department. EID, SIN are also candidate keys
It is used to uniquely define the attribute of each row.
This is a special symbol, independent of data type, which means either unknown or inapplicable, (it does not mean zero or blank)
NOTE: The result of a comparison operation is null when either argument is null. The result of an arithmetic operation is null when either argument is null (except functions which ignore nulls)
SOME IMPORTANT TERMS IN DBMS
SCHEMA of a database system is its structure described in a formal language supported by the database management system (DBMS).
DATA MINING some time called data or knowledge discovery is the process of analyzing data from different perspectives.
TABLES: Refers to data arranged in rows and columns. A spreadsheet, for example, is a table. In relational database management systems, all information is stored in the form of tables.
FIELDS: The smallest unit of information about a record in a database is called field.
RECORD: A complete set of information. Records are composed of fields, each of which contains one item of information. A set records constitutes a file.
QUERIES: In database management system, query by example (QBE) refers to a method of forming queries in which the database program display a blank record with a space for each field. You can then enter conditions for each field that you want to be included in the query.
FORM: A program that generally has more user friendly interface than a DBMS is called a from
REPORTS: A formatted and organized presentation of data. Most database management systems include a report writer that enables you to design and generate reports.
CARDINALITY: In database design, the cardinality or fundamental principle of one data table with respect to another is a critical aspect. The relationship of one to the other must be precise and exact between each other in order to explain how each table links together.
In the relation modal, tables can be related as any of “one-to-many” or “many-to-many” this is said to be the cardinality of a given table in relation to another.
DAT REDUNDANCY: Data redundancy occurs in database systems which have a field that is repeated in two or more table
DATA INTEGRITY: data integrity refers to maintaining and assuring the accuracy and consistency of data over its entire life-cycle, and is a critical aspect to the design
DATA RELIABILITY: the accuracy and completeness of computer-processed data, given the uses they are intended for
DATA CONSISTENCY: consistency, in the context of database, states that data cannot be written that would violate the database’s own rules for valid data. If a certain transaction occurs that attempts to introduce inconsistent data, the entire transaction is rolled back and an error returned to the user.
TUPLE: Tuple is the collection of information about the attributes of table for single instance. In simple this also can be called as a ‘row’ in a Table
ROLLBACK: The process of restoring a database or program to a previously defined state, typically to
IMPORTANT COMMANDS IN DATABASE:
Data Definition language (DDL) statements are used to define the database structure or schema. Some examples:
Data Manipulation Language (DML) statements are used for managing data within schema objects. Some examples:
Data control Language (DCL) statements. Some examples:
Transaction control (TCL) statements are used to manage the changes made by DML statements. It allows statements to be grouped together into logical transactions.
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