SQL

Q: What is SQL?

SQL Structured Query Languagea language designed to allow both technical and non-technical users query, manipulate, and transform data from a relational database. And due to its simplicity, SQL databases provide safe and scalable storage for millions of websites and mobile applications.

A relational database represents a collection of related (two-dimensional) tables. Each of the tables are similar to an Excel spreadsheet, with a fixed number of named columns (the attributes or properties of the table) and any number of rows of data.

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

Semicolon is the standard way to separate each SQL statement in database, systems that allow more than one SQL statement to be executed in the same call to the server.

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Important SQL Commands:

• SELECT - extracts data from a database
• UPDATE - updates data in a database
• DELETE - deletes data from a database
• INSERT INTO - inserts new data into a database
• CREATE DATABASE - creates a new database
• ALTER DATABASE - modifies a database
• CREATE TABLE - creates a new table
• ALTER TABLE - modifies a table
• DROP TABLE - deletes a table
• CREATE INDEX - creates an index (search key)
• DROP INDEX - deletes an index