SQL Overview

SQL Tutorial 2: SQL Overview

SQL (Structured Query Language) is a standard language for accessing databases.

All Relational Database Management Systems like MS Access, MS SQL Server, Oracle, Sybase, MySQL, DB2 use SQL as standard database language.
i) Environment Setup

We can practice SQL Commands in any Database Management System, Install any Database Engine like Oracle, SQL Server, Sybase, MySQL etc... and practice.
ii) SQL Syntax

•  A database contains one or more tables. Each table is identified by a name, Tables contain records (rows) with data.

•  Most of the actions we need to perform on a database are done with SQL statements.

•  SQL keywords are NOT case sensitive: select is the same as SELECT

•  All the SQL statements start with any of the keywords like SELECT, INSERT, UPDATE, DELETE etc...and all the statements end with a semicolon (;), semicolon is the standard way to separate SQL Statements.
iii) SQL Data Types

 A data type defines what kind of value a column can contain, we have to use data types while creating database tables, choose a particular data type for a table column based on our requirement.


Character Data Types,
Numeric Data Types,
Date and Time Data Types Etc...

Note: Data Types vary from One Database Management System to another
iv) Operators

Operators are used to perform Arithmetic, Comparison and Logical Operations.

Categories of Operators in SQL

1) Arithmetic Operators
2) Comparison Operators
3) Logical Operators
v) SQL Functions

SQL has many built-in functions for performing processing on data.

Categories of Built-in Functions in SQL

1) Aggregate Functions
2) String Functions
3) Date Functions Etc...
vi) Data Definition Language

The Data Definition Language (DDL) is used to create and destroy databases and database objects. 

Important Operations

 Create Database
 Use Database (Specify the Database you wish to work with within your DBMS.)
 Alter Database
 Drop Table, Drop Database
vii) Data Manipulation Language

The Data Manipulation Language (DML) is used to insert, retrieve and modify database information.

Important Operations

 Insert Records to an existing Table
 Retrieve the specific information from an operational database. 
 Modify information contained within a Table.
 Delete information contained within a Table.
viii) Data Control Language

The Data Control Language (DCL) allows database administrators to configure security access to relational databases.

Important Operations

• Provide access on the Database objects to the Users
• Remove User access rights to the Database Objects
• Deny Permissions to Users.
ix) SQL SELECT Statement

The SELECT statement is used to select data from a database.

 General Selection
 Conditional Selection Etc...
(We use clauses, Operators and keywords...)
x) SQL Joins

The SQL Joins clause is used to combine records from two or more tables in a database. 

Different SQL Joins:

1) Inner Join
2) Left Join
3) Right Join
4) Full Join
Popular Database Management Systems

1) Oracle

Oracle database is a relational database management system (RDBMS) developed by Oracle Corporation. 

Important Oracle editions are, 

i) Enterprise Edition: Offers all features, including superior performance and security.

ii) Standard Edition: Contains base functionality for users.

iii) Express Edition: The lightweight, free and limited Windows and Linux edition

iv) Oracle Lite: For mobile devices
2) Microsoft SQL Server

Microsoft SQL Server is a relational database management system developed by Microsoft.

Important Microsoft SQL Server editions are, 

i) Datacenter: SQL Server 2008 R2 Datacenter is a full-featured edition of SQL Server.

ii) Enterprise: SQL Server Enterprise Edition includes both the core database engine and add-on services.

iii) Standard: SQL Server Standard edition includes the core database engine, along with the stand-alone services.

iv) Web: SQL Server Web Edition is for Web hosting.

v) Workgroup: SQL Server Workgroup Edition includes the core database functionality only.
3) MySQL

MySQL is an Open Source Relational SQL database management system used for developing web-based software applications.

Important MySQL Editions are, 

i) Standard Edition: Standard Edition enables us to deliver high-performance and scalable Online Transaction Processing (OLTP) applications.

ii) Enterprise Edition: Enterprise Edition includes the most comprehensive set of advanced features and management tools.

iii) Cluster Carrier Grade Edition: Cluster enables users to meet the database challenges of next generation web, cloud, and communications services with uncompromising scalability, uptime and agility.
4) PostgreSQL

PostgreSQL is a powerful, open source database management system. It runs on all major operating systems, including Linux, UNIX, Mac OS X, Solaris, and MS Windows.
5) MS Access

Microsoft Access is bundled as part of the Microsoft Office suite. It is only available on the PC version. It is a desktop database system because its functions are intended to be run from a single computer.
SQL Tutorial 1: Introduction to SQL


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