Introduction to SQL

SQL/Introduction to SQL

Introduction

SQL is a tool for organizing, managing and retrieving data stored by a computer database. The name "SQL" stands for Structured Query Language. As the name implies, SQL is a computer language that you use to interact with a database. SQL works with one specific type of database called a relational database.

SQL is far more than a query tool, although that was its original purpose, and retrieving data is still one of its most important functions. SQL is used to control all of the functions that a DBMS provides for its users, including:

• Data Definition Language: SQL lets a user define the structure and organization of the stored data and the relationships among the stored data items.
• Data Retrieval Language: SQL allows a user or an application program to retrieve stored data from the database and use it.
• Data Manipulation Language: SQL allows a user or an application program to update the database by adding new data, removing old data, and modifying previously stored data.
• Access Control Language: SQL can be used to restrict a user's ability to retrieve, add, and modify data, protecting stored data against unauthorized access.
• Data sharing: SQL is used to coordinate data sharing by concurrent users, ensuring that they do not interfere with one another.
• Data Integrity Language: SQL defines integrity constraints in the database, protecting it from corruption due to inconsistent updates or system failures.

SQL is a comprehensive language for controlling and interacting with a database management system.

Why SQL?

• SQL is an interactive query language: This means that a user types SQL commands into an interactive SQL program to retrieve data and display it on the screen, providing a convenient, easy-to-use tool for ad hoc database queries.
• SQL is a database programming language: This means that a user embeds SQL commands into their application programs to access the data in a database. Both user-written programs and database utility programs (such as report writers and data entry tools) use this technique for database access.
• SQL is a database administration language: This means that a database administrator responsible for managing a minicomputer or mainframe database uses SQL to define the database structure and control access to the stored data.
• SQL is a client/server language: This means that a user SQL to communicate over a network with database servers that store shared data. This client/server architecture has become very popular for enterprise-class applications.
• SQL is an Internet data access language: This means that Internet web servers that interact with corporate data and Internet application servers all use SQL as a standard language for accessing corporate databases.
• SQL is a distributed database language: This means that distributed database management systems use SQL to help distribute data across many connected computer systems. The DBMS software on each system uses SQL to communicate with the other systems, sending requests for data access.
• SQL is a database gateway language: This means that a computer network with a mix of different DBMS products, SQL is often used in a gateway that allows one brand of DBMS to communicate with another brand.

In General, SQL has a useful, powerful tool for linking people, computer programs, and computer systems to the data stored in a relational database.

Use of SQL

• SQL (Structured Query Language) is a programming language used to query and manipulate data stored in relational databases.
• Structured Query Language is particularly utilized by business professionals or program engineers for administering, updating, maintaining, and controlling the databases or tables that are utilized for business decision-making.
• It is as a rule utilized to get data, upgrade the contents of the table, or operate on the structure of the database or tables, using any type of database tool, which can have a client interface to apply the operations on the database.
• SQL can be used for both relational and multidimensional types of databases.
• SQL is a declarative language which means it is a programming worldview, a style of building the structure and components of computer programs that express the logic of a computation without describing its control flow.

In this tutorial, you will learn the basic concept of SQL language; understand SQL syntaxes, data types, and SQL commands to filter, sort, & summarize data; manipulate strings, dates, & numerical data from different sources for analysis, and control flow. After completing this tutorial, you should have a clear understanding of the purpose of the SQL language, its usage, and how to write SQL programs.