Demystified Tech - SQL INDEPTH PRACTICAL GUIDE FOR BEGINNERS & POWER USERS

SQL is a computer language that is used for storing, manipulating, and retrieving data in databases. It was invented by IBM, and was initially named Sequel later it was renamed SQL which stands for structured query language .

In today's world, nearly all big companies or businesses are investing in technology. To gather, handle and transform a large amount of data, SQL can help us do two things with this large amount of data:

1. It can help us grant controlled access to this data.
2. You can manipulate this data so that business managers can take out vital insight from it, and make key business decisions

There are mainly three types of people that use SQL

First, the software developers or the programmers. These people create applications or programs where there is a database at the backend, these databases will then have data that the business requires

Secondly, the database manager or database administrator. These people are the operations people for that company, they manage the database of these huge companies

Thirdly, the non-IT people which are the business managers or the research analyst or evenly marketing analyst. They use this data to find out business insights, and then uses this data and information they get to take key business decisions

Now, let us see, what a database is. A database is an organized tool capable of keeping data or information that can be retrieved effectively and efficiently. A database is the collection of organized information of data stored in a table, while the table stores information in rows and columns just like an Excel spreadsheet.

There are two parts to the data being stored

The second part is the metadata , metadata defines and describes the data structure, having this information in the database will help you to retrieve the data from the database faster. You will often hear that SQL works on relational databases. Simply put, relational databases are nothing but a collection of tables, and these tables have some relationship that is, they are related in some way.

A record in a table is a row of data. An attribute is a column in the table which contains the same type of values for all the records. The intersection of these rows and columns is called a cell, and it contains a unique single value. For example, student 1 with age 18 , gender as male , score as 89, and rank as is a record. Each student comprises one record but the age of all the students is an attribute of all the students. So, age 18 is the attribute of student 1, and this 18 is a value in one single cell. Similarly, the score of 90 for student 2 is a unique value in a single cell.

Now that we know about databases, let us look at database management systems (DMBS).

DBMS is used to define, manage, and process databases. A DBMS does the following:

• It allows modification of data.
• It allows the creation of new databases and their data structures.
• You need to retrieve that data from the database using queries that are also allowed by a DBMS.
• It allows storage of data over a long period so that whenever there is data in the DBMS it is not lost easily, it just stores it for a long period.
• It enables recovery in times of failure. Whenever there is some system failure or an error, and data is lost, it enables recovery of the data.
• It controls access to users; you can define who can access the database, and who cannot.

In this guide, we will look at, classification of commands in SQL. SQL commands are classified into 5 different parts:

• Data Definition Language (DDL): This part of SQL enables you to define the structure of your data with data definition language or DDL. You can create, change or delete the existing elements of the database. In a database, there are several types of elements like tables views, schemas, etc. We will be covering only tables for now. The other three will be discussed in a separate section at the end of this segment.