Introduction to Database & SQL

It is very important to understand the database and SQL before learning any DBMS.

DATABASE

So by definition, a database is a structured collection of data. It can be accessed and manage by the user very easily. It allows us to organize data into tables, rows, columns, and indexes to find the relevant information very quickly.

Means we deal with data in our day to day life, for example: Whenever we search and sort any stuffs like clothes, groceries, home goods etc in shopping cart from an e-commerce web portal, that shopping cart is a database. Our music playlist, photo video gallery etc all are a kind of database.

The data relating to each other by nature, e.g., a product belonged to a product category and associated with multiple tags. Therefore, we use the term relational database.

In the relational database, we model data like products, categories, tags, etc., using tables which contain columns and rows. We can imagine a table similar like a spreadsheet. A table may relate to another table using a relationship, e.g., one-to-one and one-to-many relationships.

Because we deal with a significant amount of data, we need a way to define the databases, tables, etc., and process data more efficiently. Besides, we want to turn the data into information and so for this SQL (the language of the relational database) comes to play.

SQL – The language of the relational database

SQL (sequel, pronounced "ess-que-el") stands for the Structured Query Language. It is particularly useful in handling structured data, i.e. data incorporating relations among entities and variables. In short SQL is the standardized language used to communicate with a database.

According to ANSI (American National Standards Institute), SQL is the standard language for relational database management systems.

It contains three parts:

1. Data definition language includes statements that help you define the database and its objects, e.g., tables, views, triggers, stored procedures, etc.

2. Data manipulation language contains statements that allow you to update and query data.

3. Data control language allows you to grant the permissions to a user to access specific data in the database.

SQL statements are used to perform tasks such as update data on a database, or retrieve data from a database. Some common relational database management systems that use SQL are: Oracle, Sybase, Microsoft SQL Server, Access, Ingres, etc. Although most database systems use SQL, most of them also have their own additional proprietary extensions that are usually only used on their system. However, the standard SQL commands such as "Select", "Insert", "Update", "Delete", "Create", and "Drop" can be used to accomplish almost everything that one needs to do with a database.