SQL course
Understand the idea. Try the code. Take one small step forward.
01—03 · Tables & transactions
Create tables, filter rows and roll back writes in SQLite.
04—06 · Aggregation & relationships
Study grouping, joins, constraints and parameter binding.
07—08 · Indexes & reports
Read query plans and create a course progress report.
Study the mechanism, run the example, then attempt the challenge before opening the solution. Every chapter includes verification and common boundaries.
SQL: tables, rows, columns and queries
Create an isolated practice database, understand relational tables and select explicit columns.
Filtering, NULL and deterministic pagination
Combine predicates and handle missing values and sorting ties.
Writes and transaction rollback
Use precise predicates for writes and group related changes atomically.
Aggregation: COUNT, SUM and HAVING
Distinguish row filtering from group filtering and explain NULL in aggregates.
INNER JOIN and LEFT JOIN
Join courses to study records while retaining courses not yet started.
Constraints and parameterized queries
Reject invalid references and duplicate keys and understand parameter binding.
Indexes and query plans
Design an index for a query and separate correctness from performance.
Project: a course progress report
Use uniqueness and staged aggregation to build a progress report without double counting.