This article is an introduction to a Structured Query Language, which stands behind the back-end data management for popular web applications like Facebook, Instagram, WhatsApp, and others.
Let’s go through what SQL is, and what are its common practical implications.
Introduction to SQL
SQL is the abbreviation for Structured Query Language. In its most basic explanation, SQL is the most popular tool to deal with relational databases.
The database is a collection of data rows and columns.
The relational database is a database that contains data points related to each other.
Raw databases contain little insightful information for businesses, and here is when the main advantage of SQL comes in handy. It retrieves information from databases to further use in the analysis. SQL is an applicable language even if the data that it manages is analyzed by other tools like Python.
In short, the majority of activities you can perform inside the database are available with SQL. Many popular Relational Database Management Systems (RDBMS), such as Oracle, MS Access, etc. use SQL.
How does SQL work?
With SQL, users can query databases in several ways. Usually, all SQL keywords are written in uppercase. Structure query in SQL is not case sensitive but it is dependent on text lines. This means the single SQL statement should be written in one text line. When a user executes a SQL query, the system and engine of SQL work together to implement the required task. While the system is responsible for generating the best way of handling a certain task, the SQL engine implements the task.
In more detail, the process works in the following way. The SQL queries, after being written and run, are processed by a query optimizer. There are three phases that the query passes through after reaching an SQL server.
- During the stage of parsing, the system checks the syntax of the query.
- During the binding phase, there is a check of query semantics.
- Finally, during the optimization, SQL generates the execution plan for the query.
Classification of SQL commands
There are three main categories of SQL commands, which define the scope of activities you can perform with SQL.
- Data definition language contains the main commands used for organizing the data. You can use CREATE (create a new table or create new elements inside the table, such as objects or views), ALTER (modify the created elements), and DROP (delete the created elements).
- Data manipulation language contains the main commands through which you can work with records. It includes SELECT, INSERT, UPDATE, and DELETE options, through which records are created, modified, and erased.
- Data control language allows you to manage access to your database. Particularly, with GRANT you can give permission or privileges to selected users. If you want to take reverse action and cancel or take back the granted access, you should use REVOKE.
How is SQL different from Excel?
The most common association with database management is Excel, so you might question: what is different in SQL compared to Excel, and why should I learn it for dealing with databases?
Excel is a spreadsheet, not a database. Generally, they both contain data and you can manipulate them almost in the same way. However, databases have larger capacities than spreadsheets.
Firstly, spreadsheets limit users in the volume of data. Databases can contain more than a billion rows of data, whereas a spreadsheet has a limit of 1 mln rows.
Also, databases are more suitable for professional use. Via the internet connection, the database owner can give online access to many users for simultaneous work. In addition, databases can easily interact with programming languages like Python, R, or Java, to execute more powerful queries with the data.
Who is SQL for?
The scope of the SQL applications is very large. Generally, having the basic skills for dealing with business databases is a requirement for almost all professionals, as data is a powerful source for making the right business decisions and predictions. That’s why you might meet the requirements for SQL skills in the job descriptions of product manager, business analyst, marketers, etc.
Let’s go through some of the most popular occupations where SQL skills are in need.
SQL is one of the most popular programming languages that software engineers need to learn. Even if you choose to specialize in a programming language other than SQL, having a general understanding of SQL will be your competitive advantage. It will allow you to better use the business data in other programming languages.
In many companies, software engineers with SQL skills have higher salaries.
As mentioned multiple times, one of the significant advantages of SQL is that it allows it to easily manage and manipulate data. Therefore, with advanced skills in data science, you will have no difficulty dealing with large volumes of data. Data scientists with SQL knowledge are demanded in different spheres: business, technology, health, social science, etc.
Database administrators are in charge of the company’s data. They make sure there is proper storage and management of the organization’s data. In most companies, DBAs manage the team of SQL developers and rarely write SQL codes themselves. Database administrators are also responsible for proper data security.
For the kind of products, which are supposed to display company data in their end-result, SQL developers can also perform QA testing. They can apply SQL commands to access the original data and compare it with the one that is displayed.
The list of the professions where you can find SQL useful can be continued to some more 20-30 ones. In any position where you need to deal with data, SQL can help you, including professions not related to development, such as journalist, researcher, educator, etc.