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SQL : An Introduction

Sql

SQL BASIC

Sql database is very important part of our day to day life of software development.Lets have some look on  basis of Database fundamentals.

What is SQL?

  • SQL stands for structured Query Language. it is a standard query language used for managing relational Databases and performing various operations on the data.
  • It is initially created in the 1970.it is used by database administrator as well as by developers for writing data integration scripts.
  • Some common relational database management system that uses sql are: oracle, Sybase, Microsoft sql server, Access, Ingres etc.…
  • It store data in one or more objects called tables.

 

What is the use of SQL?

  • The uses includes modifying database tables and index structures.
  • Inserting, updating, deleting rows of data.
  • Retrieving subset of data from database for transaction processing and analytics applications.

 

Language Elements:

  • This language is based on several elements. For the convince all  command are usually executed through a specific SQL command line interface(CLI).
  • Clause: the clauses are components of the statements and Query.
  • Expressions: it produces scalar value or tables, which consists of columns and rows of data.
  • Predicates: if specify conditions, which are used to limit the effect of the statement and to change the flow of the program.
  • Queries: it retrieves data, based on specified predicates.
  • Statements:  statements are used for sending queries from a client program to a server where the databases are store.

SQL statement:

There are three main statements:

  1. DML
  2. DDL
  3. DCL

DML:

  • DML stands for data manipulation language.
  • Used to query and manipulate data.
  • DML includes Select, Insert, Update, Delete query.

DDL:

  • DDL stands for data definition language.
  • Used to define database objects.
  • DDL includes Create, Alter, Drop query.

DCL:

  • DCL stands for data control language.
  • Used to manage security permissions.
  • DCL includes Grant, Revoke, Deny query.

 

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