SQL Tutorials: How to Learn SQL for Beginners

SQL has gained immense notoriety in the last decade. And why shouldn’t it? It is the most preferred database language that exists. In a recent survey, SQL was rated higher than other popular database languages such as R and Python. Programmers familiar with SQL are in high demand from both data scientists and data management streams. 

So, one should ask the question: What is SQL? SQL is an acronym that stands for “Structured Query Language”. SQL is a domain-specific language commonly used in programming; it helps the programmer manage DBMS (Database Management Systems). Another notable feature of SQL is its ability to streamline processing or DSMS. It helps a programmer to handle and incorporate relationships between tables/entities and variables.

Here are some basics about SQL:

Databases To Know as a Beginner

• A Hierarchical Database is a type of database that has a tree-like structure. There is a parent node and, as further classification is made, each parent node goes on to have several child nodes. Each parent node represents a higher form or level of data, and the child nodes represent a lower level of information. The branches between both signify the type of relationship they have. 
• An Object-Oriented Database is a database type that has specific vital components known as “classes” and “objects”. The real-time instances of the classes are known as objects. This database is table-oriented. The categories in the table pertain to various functions, methods, and variables, which help establish what can be done with said data. 
• A Network Database (as the name suggests) is a network structure. This database can have multiple owners with multiple access paths. Additionally, a relationship is created between the nodes. 
• A Relational Database is the most prevalent form of database used by organizations. The data is stored in the form of records, tables, or rows. A critical piece of information for a beginner to know is that in a Relational Database, the column defines the type of data being tracked, while the rows contain the actual data. Additionally, the tables can be intertwined with other tables based on specific rules and conditions.

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The graphic below shows a database table example. Additional relationships can be created as per the needs of the developer or organization. 

What is SQL used for? What are the applications of SQL?

SQL is used for and by a majority of  industries and domains. As all organizations have data to process but not all data collected is valuable, SQL helps organizations create and synthesize relevant data. Additionally, SQL helps to identify key areas to look out for in the business.

Applications of SQL

• Within the finance industry, SQL is used predominantly to store and operate complex financial transactions, and to store the data for the users behind those transactions.
• Within musical industries, SQL is used to store various critical information about artists, their musical compositions, and other relevant data. Additionally, the relational database feature of SQL helps relate the user’s likes and preferences to the existing databases of songs and artists.
• Within social media platforms, the benefits of SQL are especially prevalent. When we create a new post or change any profile information, the database gets updated. Furthermore, all the advertisements and references that the user receives on their page are directed by SQL. 

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What is the importance of SQL?

• SQL’s greatest advantage is that it is used around the world. Whether in the professional setting or at a university, institutions around the world accept this language. Moreover, they use the language often.
• The benefit of SQL is that it is easy to learn. Compared to other syntax languages such as C++, SQL’s instructions are easy to comprehend.
• SQL benefits the users by analysing datasets and varied data. Insights from the data can be gained by using SQLs. Therefore, industries are looking for people with knowledge of SQL.
• One of the benefits of SQL language is that it is standardized, and no big changes have been observed recently in the syntax. 

The first step in learning the uses of SQL is to download the software related to the database.

Although several databases exist online, we recommend you download from one of the following databases: MySQL, MS Access, or Oracle.

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What are SQL’s most important commands?

• Select or SELECT— It is vital to know that there is no requirement to use uppercase or lowercase letters in SQL. This command extracts the data from a database.
• Update— This command allows the developer to update the existing data.
• Delete— This command deletes the selected data from the database.
• Insert Into— This command allows the user to insert new data into the database.
• Create Database— This command allows the user to create a fresh database.
• Alter Database— This command modifies the existing database.
• Create Table— This command creates a new table.
• Alter Table— This command allows the users to modify the table.
• Drop Table— This command deletes the table.
• Create Index— This command helps in creating a search key.
• Drop Index— This command deletes the index.

See below for examples of how data can be cross-referenced with the important SQL commands.

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Customer Table

Scenario 1: The developer needs to extract information about customer’s names and where they live from the columns. They’d type: SELECT Customer Name, City FROM Customer

Scenario 2: The developer wants to select all the information from the table. They’d type: SELECT * FROM customers. 

Scenario 3: The developer needs to edit a table. They would use the Insert Into function by typing: Insert Into table name (column 1, column 2, column 3, etc.) Values (value 1, value 2, value 3, and others). 

After editing the table, they need to add client names. They would type: Insert Into Customers (Customer Name, City, Country) Values (Maxwell, Melbourne, Australia).

The updated table will now look like this:

Scenario 4: A developer is told by his manager that there are some errors in the created database. He needs to correct them. This scenario highlights how SQL has an advantage over other systems. 

The error lies in the 1^st row. The city as well as the country name has to be updated to Michigan, USA.

The developer will type: UPDATE Customer SET City = ‘Michigan’, Country = ‘USA’ WHERE Customer ID = 1. 

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The updated table will look like this:

Scenario 5: A manager receives updated information from the client. He asks the developer to remove the existing client record, as that client won’t be continuing with the firm anymore. SQL’s delete syntax will help the developer accomplish their goal. 

The client Henry Ford is the record that needs to be deleted. The syntax function to use is Delete Form- Customers Where- Customer Name = “Henry Ford”. 

The updated table will now look like this:

Scenario 6: The developer wishes to delete all the records without hindering the formatting or relationship syntaxes. All they need to type is Delete From- Customers.

This command will ensure that all the data has been wiped, and now fresh information can be entered without disrupting the pre-existing relationships. 

Scenario 7: Lastly, we’ll Alter Table syntax. The CEO has required that the existing database must have the client’s phone number as well. SQL’s altering table function will do the trick. The developer will type: Alter Table- Customers Add- Phone Numbers (245).

The updated table will now look like this:

These are some of the many examples of how to use the SQL language. Keep in mind, a wide scope of syntax functions exist that are beyond the beginner level. 

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SQL’s most significant advantage is how easy it is to understand compared to other programming languages. It should take a beginner only a few weeks to learn the basics of this language. Furthermore, SQL skills are in high demand and will continue to be so for many years ahead. Data usage is only going to expand; understanding SQL can only benefit you in the long run. If you’d like to learn more about what SQL is used for and SQL’s advantages, read more about it on BYJU’S FutureSchool blog, or sign up for a FREE trial coding class with a dedicated instructor in a 1:1 environment.