Introduction to
Structure Query Language

What is SQL?

SQL is the standard programming language used for communicating, querying, updating, editing and retrieving data that is stored in relational database management systems. Standard SQL commands can accomplish all tasks right from selecting and inserting to updating and deleting. SQL statements are typically used for sending queries to a server and returning the replies to their respective client programs. Different versions of the SQL language facilitate instant access and easy manipulation for a wide range of databases.

Why Use an SQL Database

The simple structure, mix of functionality and ease of use that accompanies SQL offers a much better way of working while avoiding unnecessary complexity. Fewer commands that comprise of simple English words make SQL an easy to learn and use language for users at every level in an enterprise. Whether used for querying or data manipulation, it enables a wide range of workers to manipulate data and conduct queries independent of GUI apps. As the back-end functioning remains the same, structure query language facilitates easy switching of database applications without causing any disruption. The first preference of all major vendors, SQL continues to be a standard in relational database implementation.

What is RDBMS?

Relational database management system is the basis for modern-day database systems like SQL and MySQL. It comprises of tables, tuples, fields and column. These data items are formally described for reassembling data in different ways. Table columns contain the name and data type while rows are used for recording data for the corresponding columns.

The New Functionalities of SQL Standard

The SQL standard has undergone massive changes in the recent past. From supporting XML to expression matching to standardizing sequences, the standard edition facilitates effective management of database with minimal resources. Designed to deliver better performance and greater scalability, SQL standard edition, facilitates deeper insights across data.

Essential SQL Language Commands

Specific command line interface is used for executing essential language elements in database management systems.
Commonly used language elements are:
  • Clauses – are the components of the queries and statements
  • Statements – are used for controlling connections, transactions, sessions, program flow and diagnostics. They are used for sending client queries to the servers where the database resides. These statements are then processed by the servers and reverted to the client program. Statements enable users to execute different data manipulation procedures including complicated queries.
  • Predicates – are used for specifying conditions that limit the impact of queries and statements or for modifying the flow of a program
  • Expressions – are used for creating tables that consist of rows and columns
  • Queries – are used for retrieving data on the basis of the given criteria
  • Identifiers – are user-defined names given to tables, cursors and columns.

SQL Queries

SQL queries are used for fetching data which is delivered in the form of result tables also knows as sets. Different clauses can be used for making queries more specific. Typically executed using the “Select” statement, SQL queries also make use of the following clauses:

  • ORDER BY – used for sorting the results delivered in a random order
  • FROM - used for specifying the table which is to be searched for information
  • WHERE – used for defining rows where the search is to be carried out

SQL Data Definition

Data definition permits the user to define new elements and tables. Below are 4 commonly used data definitions:

  • CREATE – for creating a new table in your existing database
  • TRUNCATE - for deleting all the content in a table but retaining the actual table for future use
  • DROP – for deleting all the tables that are no longer in use or required
  • ALTER – for modifying the existing objects in different ways

SQL Data Manipulation

SQL queries are used for fetching data which is delivered in the form of result tables also knows as sets. Different clauses can be used for making queries more specific. Typically executed using the “Select” statement, SQL queries also make use of the following clauses:

SQL Data Control

Data manipulation allows you to modify the existing tables and add or remove information. Using the insert statement, you can also add new rows and columns to an existing table.

SQL Data Control

Data control defines the level of access granted to every table user.

  • GRANT: this statement authorizes the end-user to modify a given table
  • REVOKE: this statement takes away all the privileges that were previously granted to the end-user.

Frequently Asked Questions on Using SQL

If you have accidently deleted important data, use the SELECT command to retrieve any specific information from an operational database.