How to Learn SQL
SQL, also known as Structured Query Language, is a powerful tool to search through large amounts of data and return specific information for analysis. Learning SQL is crucial for anyone aspiring to be a data analyst, data engineer, or data scientist, and helpful in many other fields such as web development or marketing.
The good news is that SQL is easy to learn online in just one or two months—many aspiring data professionals start off with SQL and then move onto more complex programming languages like Python and R. SQL has many other benefits, including its flexibility to handle millions of rows of data and its universality across disciplines and industries. Data analysis done in SQL is easy to audit and replicate, especially when compared to spreadsheet tools.
SQL has been around since the 1970s and is here to stay. In this article, we’ll walk you through everything you need to get started in SQL.
What to know before you begin
SQL and relational databases
Many organizations use a relational database to store and process large amounts of data. With SQL (pronounced either as “sequel” or as “ess-que-ell”), you can “query,” or ask questions of, the data in a relational database. In other words, SQL is the programming language used to communicate with these databases. Each database uses its own SQL dialect but they all share the same basic syntax.
Different SQL dialects
Although all SQL languages share a basic structure, some of the specific commands and styles can differ (kind of like how different regions of the U.S. can refer to a carbonated sugary beverage as either a “soda,” a “pop,” or a “coke”). With so many SQL dialects, it can be hard to know where to start. Popular dialects include MySQL, SQLite, and SQL Server, but we recommend starting with PostgreSQL—it’s the closest to standard SQL syntax so it’s easily adapted to other dialects. Of course, if your company already has a database, you should learn the compatible dialect.
4 steps to learn SQL
Learning SQL doesn’t require prior programming knowledge, so it’s great for beginners. Devote a couple of weeks to these four steps, and you’ll be on your way to your dream analytics career.
1. Learn basic SQL syntax
You’ll need to understand the basics of SQL syntax, including the functions SELECT, FROM, WHERE, GROUP BY, HAVING, ORDER BY, and LIMIT. The different SQL dialects use very similar syntax, with a few exceptions.
With SQL, the order of written code differs from the order of execution. So you’ll need to understand proper query structure and the order in which queries must be written.
SQL Order of Execution
TL;DR: Your query will always need a SELECT and a FROM statement (to identify which columns you want returned from which table)—the others are optional.
2. Take an online SQL course
You can learn how to use SQL in production even before accessing a database. The best way to learn SQL is with hands-on courses that introduce core concepts and get you familiar with SQL code. I may be biased, but DataCamp’s Introduction to SQL course is a brilliant overview—it’s the first course in our SQL Fundamentals skill track. W3Schools’ SQL Tutorial, Codecademy’s Learn SQL course, and Khan Academy’s Intro to SQL are also excellent.
3. Start practicing with real data
The best way to master SQL is by practicing in your own environment—so you’ll need to install a database. If your company already uses a database, you should go through the proper channels to install it on your system. You (or your company) may be more comfortable working in a duplicate database that is not connected to live data at first—and that’s ok!
Then, you’ll need some data to play with. Preferably, you’d use real data from your company so you can start exploring data that matters to you. Alternatively, you can download a public dataset through Kaggle or freeCodeCamp Open Data.
4. Prepare for a job that requires SQL
So many roles today require SQL knowledge, and coding on a daily basis is the best way to become an expert. Before you start applying to jobs, you can plug any gaps in your SQL repertoire with DataCamp’s Data Analysis in SQL skill assessment. As you’re applying to positions, make sure to tailor your resume to the role to stand out. And if you land that coveted job interview, you should know how to answer the top 13 SQL interview questions.
Practice, practice, practice!
Learning SQL is like learning any other language—it takes constant practice to stay sharp and learn new things! Set aside some time every day or at least once a week to practice your SQL coding skills. Keep at it and you’ll be a SQL superstar in no time!