Weld logo

Start learning SQL

Jump in to our fun, free and engaging SQL course and become a skilled data analyst faster than you can say "left join".

Browse course content

Start from scratch with the introductory lesson, or jump to the skill you want to develop by picking the lesson you want.

Lession 1 • Introduction

Introduction: Analyzing Data with SQL

In this introductory lesson, learn what SQL is, what you can do with it, and how you can start honing your skills.

Lession 2 • Preparation

Connecting data, tables, and creating a model

The first step in getting going with SQL is connecting your data and tables and learning the architecture for building your first model.

Lession 3 • SELECTing

SELECTing your first data with SQL

The most basic SQL query grabs data from a table, and consists of a SELECT statement and a FROM statement.

Lession 4 • Filtering

Introduction to filtering (WHERE)

The ‘where’ clause in SQL is a very simple way to filter out rows in your data set based on the content of it.

Lession 5 • Filtering

Using !, =, <, > to filter data in SQL

You can use symbols like !, =, <, and > to filter data in SQL. Learn the basics of how each symbol works.

Lession 6 • Filtering

AND / OR: Filtering your data with several conditions

Learn how to combine several conditions in your ‘where’ statement by using the statements ‘and’ & ‘or’.

Lession 7 • Filtering

Filtering on non-exact values with LIKE

In cases where you're unable to define the conditions exactly, you can use 'like' clause to filter on values that match more or less.

Lession 8 • Filtering

Filtering when conditions are NOT fulfilled

To filter out based on values that are not exact, you can use the 'not' statement.

Lession 9 • Creating Columns

Introduction to columns

In this section of the tutorial, you’ll work with something new: creating new content to be included in your table.

Lession 10 • Creating Columns

Creating a new column and naming it AS something

Apart from selecting columns from the existing data, it’s also very simple to create new columns, and name them using 'as'.

Lession 11 • Creating Columns

Making calculations in columns

Creating your own columns in SQL becomes even more useful for business analysis when you include calculations in the columns.

Lession 12 • Creating Columns

Using CASE WHEN as IF statements in SQL

In SQL the ‘case’ statement functions the same way as the 'if' function in Excel.

Lession 13 • Aggregating Data

Introduction to data aggregation

This lesson introduces data aggregation. More specifically, you'll learn what to expect in this chapter and how to aggregate data.

Lession 14 • Aggregating Data


COUNT, SUM, AVG, MIN, and MAX are the SQL functions you'll use most for aggregating data.

Lession 15 • Aggregating Data


GROUP BY and ORDER BY help you summarize the results on a level in between looking at all the rows in a table and only looking at one.

Lession 16 • Aggregating Data

Avoid failing queries with aggregate functions and GROUP BY

Learn to avoid the common causes of fails when using aggregate functions and GROUP BY.

Lession 17 • Sub-queries

Introduction to sub-queries and CTE

Sub-queries and CTEs are ways to create temporary tables than can then be treated in a separate step in your query.

Lession 18 • Sub-queries


The SQL WITH clause is a CTE that allows you to create a temporary table which you can then treat in a separate step in your query.

Lession 19 • JOINing

Introduction to JOIN

Introduction to the JOIN function. Learn how to increase the width of the resulting table by adding columns from other tables.

Lession 20 • JOINing

Finding Common Identifiers & Choosing your Primary Table

Joining tables in SQL requires you to have a common identifier between tables A & B. Learn how to find it.

Lession 21 • JOINing

Using the JOIN function to combine tables

Joining tables is a way to get data from multiple tables in your SQL query. This is great if you want to query data on separate tables.

Lession 22 • JOINing

Combining CTEs with JOIN

Combining CTEs with JOINs allows you to have an even greater level of data to analyze, without unnecessarily overloading your query.

Lession 23 • Conclusion

What’s next? Start analyzing your own business data

Congratulations! You've made it through our SQL tutorial. The next step is to start analyzing your own business data.

Lession 24 • Tips & Tricks

The order of the elements in your query

In order for your SQL query to return any results, your functions should follow a specific order. Learn what that order is in this lesson.

Lession 25 • Tips & Tricks

LIMITing the amount of data with SQL

Limiting the amount of rows your SQL query returns is a nifty way to see an excerpt of your query's results (or to see if it has no errors).

Lession 26 • Tips & Tricks

Formatting best practices

Learn the various different ways you can format your SQL code to improve readability and understandability.

Lession 27 • Tips & Tricks

Documenting your code

Documenting your code ensures that you and others can go back and understand what the code is doing and how it’s structured.

Weld logo

Tired of scattered data? Sync and analyze your data with AI in minutes. Connect to 150+ apps, files and databases.

Backed by leading investors
Frontline logoCherry logoInnnovation Fund logo
Twitter LogoLinkedIn Logo
© 2024 Weld. All rights reserved.