The plan and the protocol

The plan is all 50 drills in a fixed order, easiest first, grouped into 7 tiers. Everything is numbered so you can see how many are left.

The protocol

One hour a day, 5 blocks. Works alone or with a partner.

1/5

Redo (10 min)

Take yesterday's Attempted drill. Write the query again from memory, no peeking. If you can't, read the answer once more and try again tomorrow. This block is where most of the learning happens.

2/5

New drill (30 min)

Open the next drill in the Plan. Before writing anything, say out loud what one row means and which pattern the question needs. Then write the query on paper, in the answer box, or in your own SQL window. About 25 minutes is the soft limit. There is no timer in the app.

3/5

Check (10 min)

Tap Show answer. Compare your query and your result with the real one. Then read the trap: run the broken version in your head and say why it gives the wrong answer. Optional: Copy for AI to get feedback on your version.

4/5

Wrap up (5 min)

Mark it Completed / Done (you could explain it again tomorrow) or Attempted / Retry (you didn't finish or didn't fully understand). Add one note about what tripped you up.

5/5

Buffer (5 min)

Read "What's the point?" for the drill you just did, or finish anything that ran over.

In Tier 1 the drills take 3 to 5 minutes, so do several new ones in block 2 instead of one.

The rules

6 rules

1/6

Go in order.

Don't skip ahead. Each tier uses what the one before it taught.

2/6

Say the grain first.

Before any query, say what one row means in each table you use. Most wrong answers come from counting at the wrong level.

3/6

Always ask about NULL.

For every column you filter, join or count, ask what happens when it is NULL.

4/6

Attempted is normal.

Not finishing a drill is part of the method, not a failure. "Completed" means you could explain it tomorrow.

5/6

Redo what you missed.

Redo Attempted drills within 1 to 3 days. Once a week, open More and turn on "Only attempted drills", then redo them all.

6/6

Stuck? Say the pattern before you peek.

If you have no plan after 10 minutes, name the pattern in words (anti-join, top one per group, aggregate first). Only look at the answer at about 25 minutes.

Quick refresh before an interview

Short on time? Do these in this order. They are the traps that silently give a wrong answer, and interviewers like to ask about them.

The plan

The times are rough guesses, not measurements. If a tier takes you twice as long, that is fine; adjust the pace, not the order.