X-DBMS

UNIT-3 DATABASE MANAGEMENT SYSTEMS DATA BASE A database is an organized collection of data. It is considered as a container of information. Ex.- Microsoft Access, OpenOffice.org Base, MySQL etc. Database Management System: A database management system is a software package that controls the creation, maintenance, and use of a database. TYPES OF DBMS 1. Flat File: Data is stored in a single table. Ex. MS Excel 2. Relational: Data is stored in multiple tables and the tables are linked using a common field. FLAT FILE V/S RELATIONAL DATABASE FLAT FILE DATABASE RELATIONAL DATABASE It stores data in a single table. It stores data in multiple tables Tables cannot be related. Relationship can be established. No provision of forms , query and reports. Provision of forms, query and reports. Ex: MS Excel , Libre office calc etc. Ex: MS Access , Libre office base etc. There are three types of relationships which can be created in RDBMS: 1) ONE to ONE Relationship: In this relationship, both the tables must have primary key columns. 2) ONE to MANY Relationship: In this relationship, one of the tables must have primary key column. 3) MANY to MANY Relationship: In this relationship, no table has the primary key column. Advantages of Database: 1) Reduces Data Redundancy: It reduces duplication of data i.e. same piece of data cannot be stored in two or more separate places. 2) Sharing of Data: In a database, the users of the database can share the data among themselves. 3) Data Integrity: Data integrity means that the data is accurate and consistent in the database and follows applicable standards.

4) Data Security: Database provides data security as only authorized users are allowed to access the database and their identity are authenticated by using a username and password. 5) Data security and Privacy: The DBMS ensures privacy and security so that only the authorized users can access a database according to its privacy constraints. 6) Backup and Recovery: Database Management System automatically takes care of backup and recovery. Some key features of a database: 1) A database can have one or many tables. 2) Each table in a database contains information about one type of item. 3) Every table has a key field which ensures that there are 100% unique values throughout the database. Important Terms: 1) Primary Key: A primary key is a unique value that identifies a record in a table. It helps the database to search for a record. 2) Composite Primary Key: When no field in the table has unique values to set primary key than a combination of two field is declare as primary key in the table and it is known as composite primary key. 3) Foreign key: The foreign key is a field that stores of picks up the values from a primary key field in another table to relate both tables record. 4) Alternate key: when there are more than one field having unique values for each record then only one field can be set as primary key and other field with unique values is called Alternate key. 5) Candidate key: All fields or field combinations that are eligible to be a primary key are the candidate key. DATABASE OBJECTS : 1) Table: A table is a set of data elements (values) that is organized using a model of vertical columns and horizontal rows. • Columns or Fields or Attributes: A column is a set of data values of a particular simple type, one for each row of the table. • Rows or Records or Tuples : A row also called a Record or Tuple represents a single data item in a table. Every row in the table has the same structure.

VIEWS OF TABLE Design view- it is used to define the structure of the table. Appropriate data type is assigned to the fields in the table. Datasheet view-It allows the user to enter data in the table. 2) Form: An interface that lets user view, enters, modify and delete data directly in the table. 3) Query: A query is a statement that gives you filtered data according to specified conditions. 4) Reports: It is an effective way to present data in a printed format. ***************************************************************************