Master SQL query patterns for top tech screens.
Query SQLite database tables entirely within your browser window. Practice aggregations, left joins, subqueries, and window functions through interactive challenges.
PyCodeIt Total XP
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Run interactive queries using a WebAssembly SQLite engine. No setup or hosting required.
Write SQL query statements or trace tables to predict result sets for technical tests.
All credentials and keys reside strictly in your local client. Your inputs are graded locally or via AI.
Curriculum Path
Learn relational logic step by step.
Work through the categories sequentially. Review the table columns in the schema viewer, run test queries, and evaluate your understanding of constraints and joins.
Beginner SQL
Database & SQL Fundamentals
Master relational database concepts, SQL command pillars (DQL, DDL, DML, DCL), data types, and foundational SQL syntax.
Basic Querying & Filtering
Master SELECT, WHERE, ORDER BY, LIMIT, DISTINCT, BETWEEN, LIKE, IN, IS NULL, and basic column aliasing.
Intermediate SQL
Relational JOINs
Combine multi-table datasets using INNER JOIN, LEFT/RIGHT OUTER JOINs, self-joins, and CROSS JOINs.
Aggregations & Group Filtering
Aggregate datasets using COUNT, SUM, AVG, and filter consolidated data groups using HAVING.
Built-in Functions & CASE WHEN
Manipulate text, math, and dates with built-in functions, and implement conditional log mappings.
Expert SQL
Advanced Subqueries
Leverage scalar, row, correlated and EXISTS nested subqueries to solve complex data comparisons.
CTEs & Set Operators
Structure temporary query sets with WITH CTEs, and perform operations using UNION, EXCEPT, INTERSECT.
Window Functions
Perform relative partition operations using ROW_NUMBER, RANK, DENSE_RANK, LAG, and LEAD window frames.
Database Design & Constraints
Verify normal forms, map key constraints (FK, PK, UNIQUE), and enforce referential check rules.