◀ Your Dojos SQL · Stage Select

Choose Your Stage

Four worlds. Twenty-two stages. A real database, running in this tab.

Every stage is a lesson you read, a lab you type queries into, and one graded assignment that decides whether the stage clears. Nothing to install. Stages open in order, because each one leans on the last — and clearing all 22 earns the SQL Practitioner certificate.

LVL 1Level
000000Score
0/22Stages
0Day streak
World 1

Reading Data

6 Stages

Everything you need to pull exactly the rows and columns you want out of a table: selecting, filtering, sorting, de-duplicating, the NULLs that break a naive filter, and the CASE expression that buckets rows into categories. No prior database experience assumed.

1

SELECT & FROM

Read a table, choose the columns you want, and meet the practice database you will be querying for the rest of the dojo.

SELECT FROM Schema
2

Filtering with WHERE

Cut a table down to the rows that matter, combine conditions without getting the logic wrong, and use IN, BETWEEN and LIKE.

WHERE AND / OR IN & LIKE
3

Sorting & Limiting

Control the order rows come back in, break ties on purpose, and take the top of a list — or a window out of the middle of it.

ORDER BY DESC LIMIT / OFFSET
4

DISTINCT, Aliases & Expressions

De-duplicate a column, compute new columns from existing ones, and name every output so the result reads for itself.

DISTINCT AS Expressions
5

NULL and Three-Valued Logic

The value that is not a value: why = NULL never matches, how NULL spreads through a calculation, and how to substitute it.

IS NULL COALESCE Unknown
6

CASE Expressions

SQL's if-statement. Bucket rows into named categories, get the branch order right, and never forget the ELSE.

CASE WHEN ELSE Bucketing
World 2

Summarising

In the works

Can turn rows into numbers: counts, sums and averages, grouped by any dimension, filtered after the fact, and sliced by time.

  • 2-01 COUNT, SUM & AVG
  • 2-02 GROUP BY
  • 2-03 HAVING & Filter Order
  • 2-04 Working with Dates
  • 2-05 Text & Number Functions
World 3

Combining

In the works

Can bring several tables together without losing or duplicating rows, and knows when a subquery, a CTE or a join is the right shape.

  • 3-01 INNER JOIN
  • 3-02 LEFT JOIN & Missing Rows
  • 3-03 Joining Three Tables
  • 3-04 Self Joins & UNION
  • 3-05 Subqueries
  • 3-06 Common Table Expressions
World 4

Analyst SQL

In the works

Can rank, compare a row to its neighbours, build running totals, express a funnel or a retention cohort in SQL, and change data safely.

  • 4-01 Window Functions
  • 4-02 Running Totals, LAG & LEAD
  • 4-03 Funnels & Cohorts
  • 4-04 INSERT, UPDATE & DELETE
  • 4-05 Capstone: The Monthly Report