Category Archives: SQL

Create Table Statement

CREATE TABLE Statement is used to create a New Table (Relation) in database. Table is used to store information in the database. Syntax:   Create Table command has the following form. For each column, a name and a data type must be specified and the column name must be unique within table definition. Columns are separated by colons. Not… Read More »

Data Integrity Constraints

What is Constraints? Constraints are the rules enforced on data columns on table. These are used to limit the types of data that can go into the table. This ensures the accuracy and reliability of the data in the database. Constraint could be applied at column level or table level. Column level constraints are applied only one column whereas table… Read More »

Data Types In ORACLE SQL

Oracle Database provides following basic data types for attributes defined with CREATE TABLE clause of database. Data Types Descriptions Char (N) Fixed Length Character Data. Maximum size is 255 bytes. Varchar (N) Variable Length Character Data. Maximum up to 2000 characters. Varchar2 (N) Variable Length Character Data. Maximum up to 4000 characters. Number (P,S) Numeric data type for integers and Real… Read More »

Types of SQL Statements

SQL is a special purpose programming language designed for managing data held in a Relational Database Management System (RDBMS). SQL statement includes data insert, query, update and delete, schema creation and modification and data access control. Based upon that SQL statements are divided into different categories as described below: SQL Statements Data Manipulation Language (DML) SELECT Retrieve certain record… Read More »

Relation, Attributes and Tuple

In relational database system data are represented using tables (Also known as relations.). A query issued against the DBS (Database system) also results in a table.  A table is uniquely identified by its name and consists of rows and columns. A table has the following structure: A table is consists of rows that contain the stored information, each… Read More »

What is SQL?

SQL is an ANSI (American National Standards Institute) standard computer language, which is used for storing, manipulating and retrieving data stored in relational database. SQL is the standard language for Relational Database System. History 1970: Dr.E. F. Codd of IBM (known as the father of relational database) has described a relational model for database. 1974: Structured Query Language appeared.… Read More »