SQL Tutorials

Welcome to the SQL Tutorials. The intent of these tutorials is to provide in depth understanding of  SQL Programming Language. In these tutorials, we will cover topics such as SQL Indexes, SQL syntax, SQL  Joins, SQL  Sub Queries, SQL Sequences, SQL  Date Functions, SQL Sorting, SQL Operators and many more.

In addition to free SQL Tutorials, you can find interview questions, how to tutorials and issues and their resolutions.

SQL Tutorial Overview sql tutorial

SQL is an ANSI (American National Standards Institute) standard but there are many different versions of the SQL language.

SQL tutorial gives unique learning on Structured Query Language and it helps to make practice on SQL commands which provides immediate results. SQL is a language of database, it includes database creation, deletion, fetching rows and modifying rows etc.

SQL is an ANSI (American National Standards Institute) standard but there are many different versions of the SQL language.

Index

What is SQL?

SQL is structured Query Language which is a computer language for storing, manipulating and retrieving data stored in relational database.

SQL is the standard language for Relation Database System. All relational database management systems like MySQL, MS Access, Oracle, Sybase, Informix, Postgres and SQL Server uses SQL as standard database language.

Also they are using different dialects, Such as:

MS SQL Server using T-SQL Oracle using PL/SQL MS Access version of SQL is called JET SQL (native format ) etc

Why SQL?

Allow users to access data in relational database management systems. Allow users to describe the data. Allow users to define the data in database and manipulate that data. Allow to embed within other languages using SQL modules, libraries & pre-compilers. Allow users to create and drop databases and table. Allow users to create view, stored procedure, functions in a database. Allow users to set permissions on tables, procedures, and views

SQL History

1970 -- Dr. E.F. "Ted" of IBM is known as the father of relational databases. He described a relational model for databases. 1974 -- Structured Query Language appeared. 1978 -- IBM worked to develop Codd's ideas and released a product named System/R. 1986 -- IBM developed the first prototype of relational database and standardized by ANSI. The first relational database was released by Relational Software and its later becoming Oracle.

SQL Process

When you are executing an SQL command for any RDBMS, the system determines the best way to carry out your request and SQL engine figures out how to interpret the task. There are various components included in the process. These components are Query Dispatcher, Optimization engines, Classic Query Engine and SQL query engine etc. Classic query engine handles all non-SQL queries but SQL query engine won't handle logical files.

Following is a simple diagram showing SQL Architecture:SQL Commands

Slide1

The standard SQL commands to interact with relational databases are CREATE, SELECT, INSERT, UPDATE, DELETE, and DROP. These commands can be classified into groups based on their nature:

DDL - Data Definition Language

CommandDescription
CREATECreates a new table, a view of a table, or other object in database
ALTERModifies an existing database object, such as a table.
DROPDeletes an entire table, a view of a table or other object in the database.

DML - Data Manipulation Language

CommandDescription
INSERTCreates a record
UPDATEModifies records
DELETEDeletes records

DCL - Data Control Language

CommandDescription
GRANTGives a privilege to user
REVOKETakes back privileges granted from user

DQL - Data Query Language

CommandDescription
SELECTRetrieves certain records from one or more tables

SQL References

SQL Joins

SQL Indexes

SQL Date Function