Season 1 · 30 episodes · T-SQL

The numbers lie.
Follow the joins.

Cobalt & Co. is a 12-store coffee chain whose revenue stopped reconciling after a botched ERP migration. You are the new Data Ranger. Learn SQL Server from SELECT to stored procedures — and ship the platform that proves what really happened.

Start the investigation I have an account

Free · ~1.5 hours a day · No credit card

CASE FILE · COBALT-001

-- Mira's note, found in the database
SELECT StoreID, SUM(Total) AS Revenue
FROM sales.Orders
GROUP BY StoreID;

-- Expected: 12 stores
-- Actual:   13 rows

/* The numbers lie.
   Follow the joins.  — M. */

4,200 orders1,200 duplicates5 defects

30daily lessons

5regions

5boss battles

1shipped platform

How it works

One story. One project. Thirty days.

Every lesson resolves one clue and adds one file to your portfolio. By Day 30 you have a real SQL Server project, a 3-minute demo, and an executive brief.

Read the brief

Each day opens with the story beat, the job skill, and a worked example you can run yourself.

Run the quest

Three tiers — Bronze, Silver, Gold. Write the query against the starter database and save it to your profile.

Pass the checkpoint

A short auto-graded quiz proves you understood the trap, not just the syntax. Earn XP, Shards, and Codex cards.

The season

Five regions. Escalating stakes.

ACT 1

THE LOBBY

single-table fluency. By Day 6 the student can answer any question that lives in one table, safely and precisely.

Days 1–6

ACT 2

THE DATA MINES

transform raw data into trustworthy summaries. By Day 12 the student can produce a month-end pack unaided.

Days 7–12

ACT 3

THE JUNCTION

relational thinking. By Day 18 the student can answer any multi-table business question without inflating the numbers.

Days 13–18

ACT 4

THE CLOCKWORK ARCHIVE

advanced analysis. By Day 24 the student can find patterns across time and categories, and work with semi-structured data.

Days 19–24

ACT 5

THE FOUNDRY

engineering. By Day 30 the student has a portfolio project and can defend every design decision.

Days 25–30

The deliverable

The Cobalt Data Platform

Not 30 disconnected exercises. One repo that grows every day.

A normalized schema with keys and constraints
An idempotent ETL load with a rejection table
Reporting views, stored procedures, and transactions
Indexes with before/after execution plans
Roles, row-level security, and a reconciliation test suite
A README, a 3-minute demo, and a one-page executive brief

Start Day 1

case-file.sql

SELECT cause, SUM(impact) AS overstatement
FROM (
    SELECT 'duplicate load'   AS cause UNION ALL
    SELECT 'payment fan-out'  UNION ALL
    SELECT 'timezone drift'   UNION ALL
    SELECT 'un-netted returns'
) defects
GROUP BY cause;

The revenue was never missing. It was counted more than once.

Ready to open the case?

Day 1 takes about 90 minutes. The first query takes about 30 seconds.

Create your account

The numbers lie.Follow the joins.