Skip to content

🇮🇳 Independence Day Special Offer – Learn More, Pay Less!

An illustrated desk with a laptop running a SQL query against a customer table, a SQLite jar, a schema notebook and a stack of SQL reference books

Practice lab

Stop reading about SQL. Run it.

A real SQLite database, seeded with a warehouse and a deliberately dirty ETL feed, running entirely in your browser. Write a query and see real rows.

Labs
12
Live tables
18
Graded challenges
10
Interview questions
21
Open the SQL playgroundSee the full syllabus

Nothing is installed and nothing is uploaded. The database is created in your browser and reset with one click.

How it works

Real SQLite, compiled to WebAssembly, running on your machine

Every result is genuine

Queries execute against an actual SQLite engine. Row counts, error messages and every relationship on the schema map are read from the database, not from a script written to look convincing.

The data is dirty on purpose

The source feed has nulls, duplicates, an orphan key, two date formats and a number with a comma in it. Each defect maps to a check in the validation lab.

It works like an editor

Resizable panes, a zoomable schema canvas, light and dark themes, and a Reset DB button that rebuilds all 18 tables from the seed script — so you can break anything in front of a live class.

The labs

Grouped by the course they belong to

Each lab quotes the topics from its course syllabus, so what you practise here is what the classroom sessions cover.

SQL1 month · 5 labs

Course syllabus
Query lab20 min

SQL Playground

A real SQLite engine in your browser. Write a query, press Run, and the rows come back from a real database — then open the database map to see the tables you just read from.

  • SQL fundamentals and query structure
Open lab
Query lab25 min

Joins & Set Operations

The same two tables, five different joins, five different row counts. Run them back to back and the difference stops being abstract.

  • Joins and set operations
Open lab
Query lab25 min

Subqueries & CTEs

Rewrite the same answer four ways — scalar subquery, IN, correlated subquery, CTE — and compare both the readability and the execution plan.

  • Subqueries and correlated subqueries
  • Common Table Expressions (CTEs)
Open lab
Query lab25 min

Window Functions

Aggregate without collapsing rows. Running totals, per-region ranking and month-over-month change, all on the flat sales table.

  • Window functions
Open lab
Graded45 min

SQL Challenges

Ten graded problems drawn from real ETL work. Write the query, press Check, and your result set is compared against the reference answer row by row.

  • Real-time projects
  • Interview preparation
Open lab

ETL Testing2 months · 3 labs

Course syllabus
Simulator35 min

ETL Pipeline Simulator

Run a real ETL job, one stage at a time. Every stage executes actual SQL against the live database — extract, stage, validate, transform, load, reconcile — and you can pause, step back and replay.

  • ETL concepts and testing lifecycle
Open lab
Test lab40 min

SQL Validation Lab

The six checks that make up almost every ETL test plan — metadata, record count, duplicates, nulls, column mapping and minus — each one a real query with its failures highlighted in the result grid.

  • Data validation techniques
  • SQL-based validation
Open lab
Interview30 min

Interview Mode

The questions that actually get asked in SQL, ETL testing and data warehousing interviews, with answers hidden until you have tried to answer out loud.

  • Real-time project scenarios
Open lab

PySpark2 months · 1 lab

Course syllabus
Query lab20 min

Spark SQL Basics

The Spark SQL patterns that carry over from ordinary SQL — aggregations, joins, windows and validation queries — written the way you would write them against a DataFrame view.

  • Spark SQL
  • Data validation at scale
Open lab

Data Warehousing1 month · 2 labs

Course syllabus
Visualiser30 min

Schema Visualizer

Click a dimension and watch its relationship to the fact table light up, its columns appear, and the join that uses it run for real. Then snowflake dim_product and see the same query grow two more joins.

  • Data warehouse architecture
  • Fact and dimension tables
Open lab
Simulator35 min

SCD Type Simulator

Change a customer's city and watch all three SCD types react at once: Type 1 overwrites and forgets, Type 2 expires the old row and inserts a new version, Type 3 keeps one previous value. Then drag the timeline to query the dimension as of any date.

  • Dimensional modeling
  • Fact and dimension tables
Open lab

Snowflake2 months · 1 lab

Course syllabus
Query lab20 min

Warehouse SQL Patterns

The portable half of cloud warehouse SQL — analytic aggregation, dimensional joins and incremental-load patterns — practised here before you run them against a real warehouse.

  • SQL on Snowflake
  • Snowflake architecture
Open lab

Why some courses have no lab here

Python, Automation Testing, Power BI, Databricks, Azure Data Factory, NumPy are taught in the classroom rather than in this playground. Their syllabus is not SQL-executable — a Python interpreter, a Selenium grid, a Power BI desktop file and a cloud subscription cannot be honestly faked in a browser tab, and a console that only pretends to run them would teach the wrong thing.

PythonAutomation TestingPower BIDatabricksAzure Data FactoryNumPy