How is this different from LeetCode SQL?

**LeetCode uses toy tables with 2-3 columns.** Our problems use **real production schemas (8-15 tables)** modeled after companies like Uber, Stripe, and Netflix. *You'll practice on the same data structures you'll encounter at work.*

Do I need to solve them in order?

**Recommended but not required.** Each stage builds on concepts from previous stages. *If you're experienced, you can jump to any unlocked stage.*

What SQL dialect is used?

**SQLite by default** with **PostgreSQL mode** available. The concepts translate directly to any dialect — *BigQuery, Snowflake, Redshift*.

How long does it take to complete all 50?

**Most users complete in 2-4 weeks** solving 2-3 problems per day. Total estimated time is **~20 hours** of focused practice.

How does this compare to DataLemur, StrataScratch, or LeetCode SQL?

DataLemur, StrataScratch, and LeetCode all offer SQL drilling — but none of them is built around a **curriculum**. They're catalogs. **What LDS SQL 50 gives you that they don't:** - **A 5-stage progression**, not a problem bank — each stage builds on the last, so you never have to guess what to do next - **Industry-grade 8–15 table schemas** modeled on real businesses (retail, social, fintech, healthcare), not 2–3 column toy tables - **Both SQLite and PostgreSQL in the same editor** — toggle dialects on any problem - **Built-in SQL Visualizer** that walks you through each CTE step-by-step - **AI Mentor** for unstuck moments — context-aware hints without giving away the answer - **Stage 1 is fully free** (10 problems, no signup) — try before you subscribe *If you want to drill a flat list of company-tagged questions, the catalogs are fine. If you want a path that actually builds SQL muscle memory, this is it.*

Curated Collection

Updated · May 2026

LDS SQL 50

A 5-stage progression that takes you from basic WHERE filters through window functions to staff-level multi-CTE scorecards, structured across 15 production-grade schemas so the sam….

Problems

Rounds

Datasets

~20h

Time

0/50Solved

About this collection

A 5-stage progression that takes you from basic WHERE filters through window functions to staff-level multi-CTE scorecards, structured across 15 production-grade schemas so the same pattern shows up in different domains until it sticks. The closest LDS has to a "Blind 75" for SQL — start here if you only do one collection.

Your Learning Path

5 stages — each building on the last.

Stage 1: Foundation

Locked

SELECT, WHERE, ORDER BY, LIMIT — the building blocks every query starts with.

10 problems ~3h

Stage 1: Foundation

Locked

SELECT, WHERE, ORDER BY, LIMIT — the building blocks every query starts with.

10 problems ~3h

Stage 2: Joins & Relationships

Locked

INNER joins, LEFT joins, anti-joins (LEFT + IS NULL), and multi-table reasoning. The heart of relational databases — and the bottleneck most candidates trip on first.

10 problems ~4h

Stage 2: Joins & Relationships

Locked

INNER joins, LEFT joins, anti-joins (LEFT + IS NULL), and multi-table reasoning. The heart of relational databases — and the bottleneck most candidates trip on first.

10 problems ~4h

Stage 3: Analytical Thinking

Locked

GROUP BY / HAVING, window functions (RANK, ROW_NUMBER, LAG, NTILE), running totals, moving averages, and Top-N per group. Where raw rows turn into business insights.

12 problems ~5h

Stage 3: Analytical Thinking

Locked

GROUP BY / HAVING, window functions (RANK, ROW_NUMBER, LAG, NTILE), running totals, moving averages, and Top-N per group. Where raw rows turn into business insights.

12 problems ~5h

Stage 4: Real-World Complexity

Locked

Multi-CTE pipelines, EXISTS / NOT EXISTS, UNION / EXCEPT, and date arithmetic. The production-grade patterns analysts actually ship.

10 problems ~5h

Stage 4: Real-World Complexity

Locked

Multi-CTE pipelines, EXISTS / NOT EXISTS, UNION / EXCEPT, and date arithmetic. The production-grade patterns analysts actually ship.

10 problems ~5h

Stage 5: Interview Ready

Locked

Staff-level scorecards. 3–4 CTE pipelines across 4–5 tables, combining window functions, classification, and time-series math into the same shape as a board-ready dashboard.

8 problems ~4h

Stage 5: Interview Ready

Locked

Staff-level scorecards. 3–4 CTE pipelines across 4–5 tables, combining window functions, classification, and time-series math into the same shape as a board-ready dashboard.

8 problems ~4h

Start solving — Stage 1

Why These 50?

Hand-curated for maximum interview ROI.

A Curriculum, Not a Catalog

Five stages of ten problems, each building on the last. You never wonder what to do next — Stage 1 to Stage 5 takes you from SELECT to multi-CTE business scorecards. No random pattern-jumping.

Industry-Grade Multi-Table Schemas

Every problem runs on 8–15 table production schemas modeled on real businesses — retail, social, fintech, healthcare. The same shape of query you’d actually write at a Stripe, Airbnb, or Uber.

Both SQLite and PostgreSQL

Toggle dialects with a single click on any problem. Learn the cross-dialect differences as you go, so you’re never blindsided when you switch from one company’s stack to another.

Skill Coverage

How the 50 problems distribute across SQL topics.

Filtering & Sorting

Joins

Window Functions

Aggregation

CTEs & Subqueries

Date & Time

Set Operations

CASE WHEN / Classification

Multi-CTE Scorecards

FAQ

The first 10 problems (Stage 1) are completely free.

Stages 2-5 require a Premium subscription, which gives you access to all 1,500+ problems across 15 production-grade datasets.

Ready to Master SQL?

Start with Stage 1 — graded instantly in your browser.

Start Problem 1 Browse All Problems

All company names, logos, and trademarks are the property of their respective owners. Their use is for identification purposes only and does not imply endorsement.

LDS SQL 50

About this collection

Your Learning Path

Why These 50?

A Curriculum, Not a Catalog

Industry-Grade Multi-Table Schemas

Both SQLite and PostgreSQL

Skill Coverage

FAQ

Ready to Master SQL?

LDS SQL 50 — 50 Curated SQL Problems

Problems included in LDS SQL 50

LDS SQL 50

About this collection

Your Learning Path