Most industries in today’s world, from banks to software companies, deal with a vast amount of data. Therefore, it is essential for us to know how to make sense of this massive amount of data. SQL is the most commonly used language for managing data in relational databases. By looking at the job postings on the website LinkedIn.com, we can see that in just India alone, more than 50,000 job listings mention SQL as one of their top required skills.
What Is SQL?
SQL, or Structured Query Language, is a data management language used to handle data in relational databases. With the help of SQL, you can create and modify the structure of databases and tables. You can also store, manipulate, and retrieve data from databases and tables using SQL. It is a non-procedural or declarative query language, which means that the user specifies which data is required without specifying how to retrieve it.
SQL is a standard language of the International Organization of Standardization (ISO) and one of the most sought after skills in the industry.
Now that we have the answer to the “what is SQL” question, let’s see why it is important in the modern world.
Importance of SQL
The Most Popular and Universal Database Language
SQL is the language most professionals turn to when it comes to handling data. The most popular open-source databases support SQL, making it the most commonly used relational database language.
Easy to Learn
Because SQL is a query language and not a programming language, it is comparatively easier to grasp than any other language with a syntax similar to logical English sentences.
Standard Relational Database Language
Both ANSI and ISO standardized SQL. It hasn’t changed much over the years, and once you learn SQL, you won’t have to worry about keeping up with too many changes in the years to come.
Helps You Understand Your Dataset
You can use SQL commands to obtain a detailed understanding of your dataset, which is crucial in order to retrieve any useful information from it.
Handle Massive Datasets
SQL can handle large datasets that Excel and regular spreadsheets cannot.
If you’re aspiring to work in data analytics or data science, SQL is one of the fundamental skills you’ll need to have.
The Need for SQL
In the early 1970s, IBM had developed two non-relational methods of storing and retrieving data called ISAM and VSAM. Using these methods, you could perform elementary operations, such as storing, deleting, and retrieving one record at a time.
In 1973, IBM started working on a relational database language based on Edgar F. Codd’s relational model paper published in 1970. They named this language SEQUEL, which was later changed to SQL. In 1979, Oracle released the first commercial version of SQL, which was based on the IBM version.
SQL has an edge over previous data handling methods for the following reasons:
- Users can access multiple records of data with a single line of command.
- Users have a clear understanding of the internal structure of data, enabling them to perform complicated queries based on it.
- It provides data security and integrity.
- There is no need to specify how to get the data.
- The syntax is easily understandable and similar to the English language.
The conception of SQL revolutionized the world of data, and that is why it remains at the number one position, even after 40 years of its existence.
Let’s move on to how you can start learning and practicing SQL yourself to get an even clearer picture of what SQL is.
How to Start Practicing SQL
To start practicing SQL, you need to have a Relational Database Management System (RDMS) on your device. You can choose from a wide variety of popular open-source databases available online, the most popular of which is MySQL. It is free and compatible with a variety of operating systems, such as Windows and Linux, and it is simple to install.
The steps to download MySQL on your device are as follows:
- Visit the following URL: https://dev.mysql.com/downloads/mysql/
- Select your device’s operating system from the drop-down list.
- From the list of available versions that appear, download the most suitable version for your device.
- Once the installation of the version of MySQL you selected is complete, you’re all set to start practicing SQL.
To properly understand what is SQL, you need to know about the SQL commands.
Syntax and Basic SQL Commands
To perform all the required commands, SQL consists of the following sub-languages:
Data Definition Language (DDL)
This includes commands like CREATE and DROP, which enable the creation and modification of database objects, such as tables.
Data Manipulation Language (DML)
DML is used to store and modify the data in the database. Commands like INSERT and SELECT belong to this sub-language.
Data Control Language (DCL)
This sub-language comes into play when you want to control the access to your database using the commands GRANT and REVOKE.
Transaction Control Language (TCL)
TCL is used to handle the modifications that DML commands made to the data by using the COMMIT and ROLLBACK commands.
Let’s see how some of these commands work. The first thing we need to do is create a database, which is a collection of structured data stored in any electronic device that a relational database management system oversees.
To create a database, we’ll use the CREATE command. CREATE is a DDL command, and it is used for the creation of both databases and tables. The syntax of the CREATE command is as follows:
CREATE DATABASE database_name;
The name of the database you create should start with a letter and contain only alphanumeric characters and underscores. We'll create a database called our_first_databse and then begin adding objects to that database.
CREATE DATABASE our_first_databse;
To check whether our database was successfully created or not, we can use the
SHOW DATABASES command.
As you can see, our database has been successfully created.
- To use this database, we’ll use the following command:
- Now that we have our database, our next step would be to create a table and populate it.
A table is a collection of rows and columns in which every column represents an attribute and has a data type, and every row is an instance in the table.
We must use the following command to create a table:
CREATE TABLE table_name (column datatype);
SQL has the following six categories of pre-defined data types that you can use:
- Numeric data types, like int and float.
- Date/Time data types, such as Timestamp and Date.
- Character/String data types, such as Char and Varchar.
- Binary data types, including Binary and Varbinary.
- Unicode Character data types, such as NChar and NVarchar.
- Other miscellaneous data types, like Clob and XML.
We’ll create the following table in our database:
The data type of the attribute “Name” is varchar(250), so this attribute will contain a maximum of 250 characters. Attributes “ID” and “Salary” will only contain integers.
- To populate the table we just created, we’ll use the INSERT command, which is a part of the DML sub-language.
The syntax of the INSERT command is as follows:
INSERT INTO table_name (column1, column2…)
VALUES (value1, value2…);
Now, we’ll populate our table “Person” using the following command:
This will result in the following table:
Now that we’ve populated our table, we’ll use the SELECT command to retrieve information. The following is the syntax of the SELECT command:
SELECT column FROM table_name;
If you want to retrieve all the records from a table, you can use the following command:
SELECT * FROM table_name;
Using the example from our “Person” table, we’ll retrieve the attributes “ID” and “Name” using the following command:
SELECT ID, Name
The output of the above command will be as follows:
- Occasionally, you need to delete records from the table you created.
The DELETE command from the DML sub-language can be used to delete a row or a set of rows from a table. The syntax of the delete command is as follows:
DELETE FROM table_name
The DELETE command contains a WHERE clause, enabling users to specify the condition according to the rows they want to delete. If there aren't any specified conditions, all the rows from the table will be deleted.
For example, if you want to delete all the records that contain salaries less than or equal to Rs. 20000 from our “Person” table, you can use the following query:
The above query will result in the following output:
- There is another command in the DDL sub-language that deletes the table or the database from the memory permanently.
The DROP command carries out this function. The syntax is as follows:
DROP DATABASE database_name;
DROP TABLE table_name;
The following command will erase our database, our_first_database, permanently:
DROP DATABASE our_first_database;
Now, we have deleted the database we created, including all of its contents. We can use the SHOW DATABASES command to confirm this.
With this, we reach the end of this “what is SQL?” article.
Learning SQL can potentially open up doors to lucrative careers and trending positions, such as business analyst, data analyst, NET developer, data scientist, and many more. All of these exciting opportunities can either benefit from, or require, learning SQL skills. It is also the standard database language utilized in the most popular database systems, such as MySQL, Oracle, and MS Access.
Now that you know the basics of SQL, you’ve taken your first step towards becoming an expert in SQL. If you liked this article and want to get certified, you can check out Simplilearn's Business Analyst Master’s Program, which also covers SQL in great depth.
Do you have any questions for us? Be sure to leave them in our comments section, and we’ll have our experts in the field answer them for you.