Learn SQL Online: Free Roadmap and Quick Reference

SQL is the language used to pull data out of databases. If you work with data, reporting or business analysis, it is the natural next step after Excel. Cellgrids is adding a full SQL section, built the same way as the Excel side: short explanations, real examples and practice that checks your work. This page shows what is coming, and gives you a quick reference to start with today.

What is available and what is coming

Live now

SQL interview questions116 questions with answers on joins, GROUP BY, window functions, CTEs and more. Open the SQL interview questions.

Step-by-step SQL lessonsFrom SELECT to joins and subqueries, with short examples you can run.

Live SQL editorWrite a query in your browser and get it checked, like the Excel practice sheet.

Window functions practiceRanking, running totals and month-over-month questions with answers.

SQL certificationA certificate you can verify, like the Excel one.

Open SQL interview questions →Excel interview prep

SQL quick reference: the commands you will use most

Most analyst work uses just these seven ideas. The examples use standard SQL, and small differences between databases are noted where they matter.

SELECT: choose columns

SELECT name, city FROM customers;

Reads columns from a table. Use * for all columns, but naming columns is cleaner and faster.

WHERE: filter rows

SELECT * FROM orders WHERE amount > 500 AND status = 'Paid';

Keeps only the rows that meet your conditions. Combine conditions with AND and OR.

ORDER BY and LIMIT: sort and cut

SELECT * FROM orders ORDER BY amount DESC LIMIT 5;

Sorts the result and keeps the first few rows. SQL Server uses TOP 5 instead of LIMIT 5.

GROUP BY: summarise

SELECT region, SUM(amount) AS total
FROM sales
GROUP BY region;

Turns many rows into one row per group. Think of it as a PivotTable in code. Use HAVING to filter the groups.

JOIN: combine tables

SELECT c.name, o.amount
FROM customers c
JOIN orders o ON o.customer_id = c.id;

Matches rows between tables on a shared key. LEFT JOIN keeps all rows from the first table even when there is no match.

CASE WHEN: if-then logic

SELECT name,
  CASE WHEN score >= 50 THEN 'Pass' ELSE 'Fail' END AS result
FROM students;

SQL's version of the Excel IF function.

Window function: rank without grouping

SELECT region, amount,
  RANK() OVER (PARTITION BY region ORDER BY amount DESC) AS rnk
FROM sales;

Calculates across related rows but keeps every row. Used for rankings, running totals and month-over-month change.

A good order to learn SQL

SELECT, WHERE, ORDER BY and LIMIT
Aggregates: COUNT, SUM, AVG, MIN, MAX with GROUP BY and HAVING
JOINs: INNER and LEFT first
CASE WHEN, handling NULLs with COALESCE, and working with dates
Subqueries and CTEs
Window functions: ROW_NUMBER, RANK, LAG and running totals

Already know Excel?

You have a head start. A filter in Excel is a WHERE in SQL, a PivotTable is a GROUP BY, VLOOKUP and XLOOKUP are joins, and IF is CASE WHEN. Practise your Excel on the live spreadsheet, and try the Excel formulas cheat sheet.

Frequently asked questions

Is SQL hard to learn?

No. SQL reads close to plain English, and most analyst work uses a small set of commands: SELECT, WHERE, GROUP BY, JOIN and a few window functions. Most people can write useful queries in a few weeks of regular practice.

Do I need to know SQL if I already know Excel?

It helps a lot. Excel is great for small data and presentation, but SQL is how you pull data from databases that are too large or too connected for a spreadsheet. Data analyst, business analyst and MIS roles often ask for both.

What will Cellgrids offer for SQL?

The plan is step-by-step lessons, a live SQL editor that checks your query, window function practice, interview preparation and a certification, built the same way as the Excel side. The 116 SQL interview questions are already live.

Which SQL database should I start with?

The basics are the same in MySQL, PostgreSQL, SQL Server and SQLite. Learn the standard commands first, then pick up the small differences in the database your job uses.

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