How I Would Learn SQL Starting Today

The Only Complete Roadmap You Need to Master SQL

Photo by Sunder Muthukumaran on Unsplash

Are you trying to learn SQL in a short period?

However, you are still unsure about “how you should begin”. For example, what topics should I begin my learning journey with?

We've all been there. Is it still worth learning SQL, though?

SQL (Structured Query Language) is the foundation of data management and analysis in all businesses. So, whether you're a data analyst, a business analyst, or a software developer, SQL is essential for thriving in your professional career.

In this article, I'll outline the steps you should follow to learn SQL, regardless of your role. It applies to everyone.

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Step 1: Start With Database Fundamentals

According to what I have noticed, most people begin learning SQL with operations such as SELECT, WHERE, and so on.

But, ask me. I would say it is not a good start. Before any of this, I want you to ensure that your fundamentals are so solid that no one can destroy you.

What exactly are the fundamentals? - Database fundamentals.

You must understand all of the essential concepts of SQL and relational databases:

1. Learn about databases and tables:

To fully understand databases and tables, you need to ask the following questions:

1. How data is organised in relational databases?

2. What is a database?

3. What is a table?

4. What is an entity?

This will provide you with a basic overview of databases, tables, entities, and their relationships.

2. Familiarize yourself with data types:

Now you understand how the data is organised and structured. You ought to find out: “What are the data types that we can store so that SQL supports them?”

Answer to this:

SQL supports the following data types for improved efficiency:

1. Numeric: INT, DECIMAL, FLOAT

2. String: VARCHAR, CHAR, TEXT

3. Date and time: DATE, TIME, TIMESTAMP

4. Boolean: BIT, BOOLEAN

3. Study design principles of database:

I recommend that you read and learn about the following database design principles:

1. Primary Keys

2. Foreign Keys

3. Data Normalisation

Why am I asking you to study these database design principles?

The only reason is that I want you to understand how to organize data to reduce redundancy and dependency for better performance.

4. Understanding Constraints:

Finally, don't forget to understand database constraints. Why? - Because we will utilize these constraints regularly in real-world applications to ensure and protect data integrity.

Some of the constraints are:

1. PRIMARY KEY (uniquely identifies a row in a table)

2. FOREIGN KEY (builds relations between tables)

3. UNIQUE (makes sure all values in a column are distinct)

4. CHECK (enforces specific conditions on data)

5. DEFAULT (assigns a default value for a column)

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Step 2: Time for Basic SQL Operations

We're done with the theoretical part. It's time to get our hands dirty with SQL operations while keeping the theory in mind.

For this phase of learning, I recommend hands-on practice rather than just reading and studying about it.

Here are the essential SQL operations that serve as the foundation for data manipulation:

1. SELECT statements

2. Filtering with WHERE

3. Sorting with ORDER BY

4. Data manipulation using INSERT, UPDATE, and DELETE

5. Finally, LIMIT and OFFSET

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Step 3: Explore Through Advanced Querying Techniques

Once you've covered the basics, you can progress to more advanced operations. - (done! done!)

What I mean by "done" is that you should now understand how SQL queries undergo execution in order. This comes only with regular practice.

If you still don't understand the order in which SQL queries are executed, read this article.

How SQL Queries Are Executed And How You Can Optimize It

After you've completed all of the preceding steps, your next step should be looking into advanced query techniques.

Keep in mind that these questions are regularly asked during technical interviews.

Here are the techniques:

1. JOIN : The JOIN statement is used for combining data from multiple tables. If you wish to understand more about this topic. This is one of my best-performing pieces; read it here.

2. Subqueries: Subqueries are the process of nesting queries within other SQL statements.

3. Aggregate functions: These functions summarize data by conducting calculations. You should practice utilizing some of the most common functions, such as COUNT, SUM, AVG, MIN, and MAX.

4. GROUP BY and HAVING : This allows you to group data based on a specified column and filter it using aggregated data.

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Step 4: Remember the use of these functions

If you have completed all of the steps listed so far. I’d say you can now solve practically any SQL interview question.

However, if you want to learn more and become an SQL expert. There are a couple more steps.

The next step is to practice and apply these SQL functions to improve your data manipulation skills:

1. String functions: To manipulate text data

   • CONCAT

   • SUBSTRING

   • UPPER / LOWER

   • LENGTH

2. Date and Time functions: For working with temporal data

   • GETDATE

   • DATEADD

   • DATEDIFF

   • DATEFORMAT

3. Numeric functions: For mathematical operations like rounding and ceiling.

   • ROUND

   • CEILING / FLOOR

   • ABS

4. Conditional functions: Specifically to use IF/ELSE logic in SQL.

   • CASE WHEN

   • COALESCE

   • NULLIF

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Step 5: Database Management

This is the point where you move beyond querying and manipulation. This is where you'll learn how to manage databases.

Why should you learn data management?

1. You will be able to create and modify database structures.

2. You'll be able to optimize your query performance.

3. You will be able to generate virtual tables based on the results of a SQL query.

4. Finally, you'll be able to generate reusable SQL code.

So, What do you need to learn?

1. DDL (Data Definition Language)

   • CREATE TABLE

   • ALTER TABLE

   • DROP TABLE

2. Indexing

3. Views - CREATE VIEW

4. Stored Procedures - CREATE PROCEDURE

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Step 6: The Final Ultimate Concepts

These concepts are not always needed yet if you understand these, you know more than 85% of the professionals in SQL.

So, the ultimate concepts are:

1. Transaction: It is the concept that you need to learn to deal with transactional data.

   • ACID properties

   • Managing transactions - COMMIT, ROLLBACK, and SAVEPOINT

2. Query Optimization: This is to improve the performance of your SQL queries. Learn more about it here.

3. Data Control Language (DCL): This is to understand how to manage database access.

   • GRANT

   • REVOKE

4. Finally, CTEs, or Common Table Expressions. This concept is critical for understanding how to build more understandable and maintainable complex queries.

So, that's all you need to master SQL. If you truly want to master, it will take time and a lot of practice.

My advice is to start with basic queries and then work your way up to more complex techniques.

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