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BASIC RDBMS CONCEPTS

Index

1. what is RDBMS

2. Database concepts3. Explanation4. Database three tier architecture5. Relational Model6. E-R Diagram7. E-R Diagram (Explanation)8. E-R Diagram (Explanation)9. Rules for RDBMS10. Keys in RDBMS11. Keys in RDBMS(continue)12. SQL in RDBMS13. Basic Datatypes in SQL

Index

14. Operators in SQL - Arithmetic

15. Operators in SQL - Comparison16. Operators in SQL - Logical17. Operator with Examples - comparison operator18. Operator with Examples - LIKE operator19. Operator with Examples - AND operator20. Operator with Examples - IN operator21. RDBMS Databases - MYSQL22. RDBMS Databases - MS SQL Server23. RDBMS Databases - Oracle

What is RDBMS

RDBMS - Relational Database Management System

It is database management system based on relational model , which is used to manage relational database. Relational model is organization of data in tables which are interrelated. Relational Database It is organized collection of tables. Data is stored in tables. Tables are related to each other using one or more fields.

.

Database concepts

Table A table is collection of rows and columns. In RDBMS table is called Relation and rows are called as tuple. Record A single row in a table is called record. It is also referred as tuple. It is a collection of fields. Column It is collection of field values of same type. Field It contains data. The smallest entity of table is field.

Explanation

For Example table STUDENT Row column

student_id Student_name marks 1101 abc 80

1101 Abc 80

Student_id1101

1102

Database three tier architecture

Relational model

In relational model , each table is related to every other table in database. There is one common field in tables which is used to relate them. Dept_no field that relates department table and professor table.

E-R Diagram

The Entity Relationship Diagram

Explanation

Entity An Entity represents a real world thing. For example student and class are entities. In E-R diagram rectangle shape is used to represent entity. Attribute The characteristics of an entity are called attributes. Student is entity . It has name , id , course he/she opts for are attributes. first_name

Student

Explanation

RelationshipIt describes how two entities are related to each other

Enrolls in Class

key attribute It is the main characteristic of an entity. It is used to relate tables student_name student_id key attribute

Student

Student

Rules for RDBMS

Codd's twelve rules are a set of thirteen rules (numbered zero to twelve) proposed by Edgar F. Codd, a pioneer of the relational model for databases, designed to define what is required from a database management system in order for it to be considered relational, i.e., a relational database management system (RDBMS)They are sometimes referred to as "Codd's Twelve Commandments". A DBMS is said to be Relational Database management If it follows Codd’s rules. Practically all rules are not followed , but RDBMS follows maximum of he Codd’s rules

Keys in RDBMS

Primary KeyAn attribute that is used to access the table data is called primary key. It mustContain Unique values. It uniquely identifies a record in a table.

Candidate KeyIt is set of attributes from which primary key is selected. One of them is made asPrimary key and rest are candidate keys. They are candidate for primary key.It uniquely identifies a record.

Composite keyWhen more than one attributes are used to uniquely identify a record in a tableIt becomes composite key.

Keys in RDBMS

Super Key

It is a set of attributes that uniquely identifies each record in a table. It is a superset of candidate key.

Secondary Key

The candidate keys which are not selected as primary key , are called as secondary key or alternate key.

SQL in RDBMS

Structure Query Language(SQL) is a programming language used for storing and managing data in RDBMS. SQL was the first commercial language introduced for E.F Codd's Relational model It is used to perform all types of database operations. Almost all database use SQL as standard language for manipulation of data. It is case sensitive language. SQL is set of three data languages. These are

DDL - Data Definition Language. It is set of commands for defining table in database DCL - Data Control Language. It is set of commands used for controlling access to database DML - Data Manipulation Language. It is set of commands used to manipulate table data.

Basic Data types in SQL

Char Takes Fixed length string 1 byte to 1000 bytes

Varchar Takes variable length string 1 byte to 4000 bytes

Varchar2 Takes variable length string 1 byte to 4000 bytes

Number It stores fixed and floating point numbers

up to 38 digit precision

Date It stores date values in dd-mm-yyformat

as required

Boolean It takes true or false value Only two values T or F

Operators in SQL - Arithmetic

Operators in SQL – comparison

> Greater than Checks if the value of left operand is greater than the value of right operand

(a > b)

< Less than Checks if the value of left operand is less than the value of right operand

(a < b)

<> Not equal to Checks if are equal or not. (a <> b)

= Equal to Checks if the values of two operands are equal. (a = b)

Operators in SQL - logical

ALL The ALL operator is used to compare a value to all values in another value set.

ANY The ANY operator is used to compare a value to any applicable value in the list according to the condition.

BETWEENThe BETWEEN operator is used to search for values that are within a set of values, given the minimum value and the maximum value.

IN The IN operator is used to compare a value to a list of literal values that have been specified.

LIKE The LIKE operator is used to compare a value to similar values using wildcard operators.

Operators with examples

Table student

comparison operator <= SELECT student_name , stu_id from student where marks >= 85 output – David 1102

Student id Student name

course marks

1101 John oca 80

1102 Rohit scjp

85

1103 Ramesh mca 82

Operators with examples

Like operator SELECT * from student where student_name LIKE ‘r %’ ; * means all fields.

output – 2 rows in which names begin with letter ‘r’

1102 Rohit scjp

85

1103 Ramesh mca 82

Operators with examples

AND operator – It is used to join two or more conditions. Output are the rows That satisfy all conditions given in statement SELECT student_id from student where marks > 80 AND student_name LIKE ‘r%’ ; output – we have given only one field to select i.e... Student id. Those student ids who have name begin with ‘r’ and marks greater than 80.

1102 1103

Operators with examples

IN operator SELECT course from student where name IN (‘ramesh’ , ‘rohit’ ); It searches rows and takes only those values of course in which name is ramesh and rohit. Output

Equivalently : SELECT course from student where name = ‘ramesh OR name = ‘rohit’; For multiple OR conditions we can use IN operator.

SCJP MCA

RDBMS Databases

The following Databases are Relational Database Management System MySQL MySQL is an open source SQL database, which is developed by Swedish

company MySQL AB. MySQL supports many different platforms including Microsoft Windows, the major Linux distributions, UNIX, and Mac OS X.

MySQL has free and paid versions , depending on its usage (non-commercial/commercial) and features. MySQL comes with a very fast,

multi-threaded, multi-user, and robust SQL database server.

RDBMS Databases

MS SQL Server Microsoft SQL Server is a relational database management system developed by Microsoft. As a database server, it is a software product with the primary function of storing and retrieving data as requested by other software applications which may run either on the same computer or on another computer across a network (including the Internet). MS SQL Server is a Relational Database Management System developed by Microsoft Inc. Its primary query languages are: T-SQL. ANSI SQL.

RDBMS Databases

ORACLE It is a very large and multi-user database management system. Oracle is a

relational database management system developed by 'Oracle Corporation'. Oracle works to efficiently manage its resource, a database of information,

among the multiple clients requesting and sending data in the network. It is an excellent database server choice for client/server computing. Oracle

supports all major operating systems for both clients and servers, including MSDOS, NetWare, UnixWare, OS/2 and most UNIX flavors.