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How does SQL Database work?

19.06.2021

To begin with, how SQL Database works, you must know what SQL Database is? SQL stands for Structured Query Language which is a basic English programming language used for managing relational databases by performing a query with a database. Many databases support the use of SQL to access their data. The data management comes into play when the SQL client communicates with a database and it is used to create/collect/store data, update or delete that data, extract that data, and manage user permissions to that data. It is also used to retrieve data from a database. This entire system is called the relational database management system(RDMS).


What Is SQL?

Data is an important part of almost all web applications and mobile apps. For example, an application like Instagram holds a user’s profile information, including data about their followers/followings, posts, and whatnot. To store all this data, a database system is used. 

SQL is a programming language that enables programmers to work with that data. Many other businesses will use some form of a SQL server for their relational database environment because of the easy backup, recovery, flexibility, scalability, reduced redundancy, and standards compliance. 


What is “Query” SQL

Structured Query Language abbreviated as SQL, is a special programming language used to manage databases. An instruction issued by SQL to the database server for retrieving data is known as a query.

A typical SQL query looks like this:

SELECT * FROM PerfectElearning WHERE Employees = 23;

Apart from retrieving the data from tables, SQL can update, insert and delete the data from tables and even create new tables. This is how applications store and edit all your data by storing and retrieving it from the database using SQL queries.


SQL is used to:

  • Run queries in a database

  • Obtain information from a database

  • Insert data in a database

  • Update data to the records in a database

  • Remove data from a database

  • Make new databases or tables in an existing database

  • Create stored procedures and views in a database

  • Set permissions for tables, procedures, and views in a database


What is the benefit of learning SQL basics?

It is a highly demanding tool for Machine learning, data analysts, data scientists, and a wide variety of professionals in other roles, including Development, marketing, finance, HR, sales, and much more.

SQL is the most important language for getting a job in IT, and that’s not it- since most companies store their data in SQL-based databases, anyone who works with the company’s data can benefit from learning SQL.

We hope you all got an overview of SQL now we're going to take a look at how SQL works in practice

But first, let’s take a look at some of the frequently used SQL commands :

  • SELECT – extracts data from a database

  • DELETE – deletes data from a database

  • UPDATE – updates data in a database

  • ALTER TABLE – modifies a table

  • DROP TABLE – deletes a table

  • CREATE TABLE – creates a new table

  • CREATE INDEX – creates an index (search key)

  • DROP INDEX – deletes an index

  • INSERT INTO – adds new data to a database

  • START TRANSACTION – used to start a transaction.

  • COMMIT – this command is used to apply modifications and close the transaction.

  • ROLLBACK- is used to undo modifications and complete the transaction.

  • REPLACE – it is used to add or update (or replace) existing or new data.

  • TRUNCATE – it is used to clear (or erase) all data from a template.


What is the source of the data?

Let's start with a general overview of how data comes to a SQL client. 

Although there are several methods for gathering and organizing data, the principles remain the same. When data is sent to a server, a data storage system, such as one based on the Apache or Nginx platforms, can convert it into tables and store it in a data warehouse server for SQL to access. Normally, this is accomplished by transforming the data. Because we don't want to write directly to the database, we normally convert the data to a format that the database can understand (such as a JSON file). The database warehouse is the main database engine that connects and communicates with SQL clients. The SQL request is forwarded to an application server by the database warehouse to obtain data. The application server then processes the data and transmits it to a web server, which converts it into user-friendly SQL data tables.


Stages of Compilation for the SQL Database Engine

How a query compiles and executes in SQL has its stages. 

The classification for these SQL processing steps differs depending on the client, but it's usually referred to as a SQL driver or SQL statement. The processes are compiling, optimizing, and executing, according to SQL Authority's diagram.

According to Microsoft, the SQL statement is processed by the RDBMS by:

  • Compiling (Parsing): The sentence is tokenized into individual words with valid wording and phrases.

  • Compiling (Checks semantics): Validates the statement by comparing it to the system's catalogue to determine if the databases, tables, and columns the user needs are available and if the user has permission to execute the SQL query.

  • Compiling (Binding): Creates a query plan for the statement, which is a binary representation of the steps needed to execute it. It will be byte code in all SQL server engines. A command line shell — a programme that reads SQL statements and transmits them to the database server for optimization and execution is developed.

  • Optimizing: Optimizes the query strategy and selects the optimal algorithms for searching and sorting, among other things. The Query Optimizer or Relational Engine is the name of this feature. After that, we'll have a prepared SQL statement.

  • Executing: The query plan is used by the RDBMS to execute the SQL statement.


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    How SQL Database Engines Work?

      1. Before the SQL engine can handle a user's request in a valid query/database language, it must be translated into a SQL request. The SQL storage engine writes to and retrieves data from a data warehouse server, which is frequently accomplished by transforming the data to a compatible format, such as a JSON file.

      1. The query processor accepts, parses, and executes SQL queries for the data warehouse to transmit to an application server to obtain the data. The SQL request is processed by the application server and sent to a web server, where the client can access the information through SQL data tables.

      1. Data is processed in phases by the SQL engine. The phases of processing differ depending on the client, but in general, the RDBMS parses a SQL query via a parse call to prepare it for execution. The statement is divided into a data structure that other procedures can process, and three tests - syntax, semantic, and shared pool check are done.

      1. The query optimization process is the next stage. The query is optimized, and the finest strategies for searching and sifting through data are chosen by the RDBMS. Finally, the RDBMS runs the query plan to execute the SQL statement.

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          Conclusion

          This blog contains all of the fundamental knowledge regarding SQL and how SQL databases work. Moreover, we hope the updated basic commands, most recent SQL version queries will help you strengthen your basic knowledge of SQL Database. Without a doubt, SQL is the most sought-after skill for the data analytics field or data science professional.