Changelog
All notable changes to the SQL Engineering Handbook will be documented in this file.
The format is based on Keep a Changelog,
and this project adheres to Semantic Versioning.
[Unreleased]
Added (2026-10-19)
- Published Module 17 — Transactions & Concurrency Control: 7 lessons (ACID, isolation levels, locking mechanisms, deadlocks, MVCC, anti-patterns, transaction design workflow), diagrams, practice problems, and SQL demo scripts. Present in
17_TRANSACTIONS_AND_CONCURRENCY/. Module README documents which demo steps were reproduced and which steps require owner-side verification.
- Published Module 18 — SQL Interview Questions: 92-question bank across competency levels 0–9, taxonomy, question index, and a structural validator script. Present in
18_SQL_INTERVIEW_QUESTIONS/. FINAL_VALIDATION_REPORT.md documents module-level structural validation; full cross-module link verification and live SQL execution were not performed as part of this change.
Added
- Added the Query Optimization module with execution-plan analysis, indexing guidance, query rewrites, benchmarking examples, CI support, and practical performance workflows. (2c510a0 — 2026-09-[…]
- Added comprehensive learning resources for books, blogs, documentation, videos, interview preparation, newsletters, courses, datasets, playgrounds, certifications, communities, and SQL tools, wi[…]
- Added extensive Views lessons covering view fundamentals, lifecycle, security, maintainability, performance, and practical examples. (daf26d0 — 2026-09-12)
- Added extensive Set Operators lessons covering UNION, UNION ALL, INTERSECT, EXCEPT, comparison patterns, and practical examples. (b108c42 — 2026-09-02)
- Added expanded Advanced Aggregations lessons with navigation, diagrams, and additional business-oriented examples. (d9b0b6b — 2026-09-01)
- Added expanded String Functions lessons with module navigation, diagrams, examples, and reference material. (33267a1 — 2026-08-27)
Changed
- Improved the Resources library README with a complete library map, build status, module checklist, file metrics, diagrams, roadmaps, and corrected folder structure documentation. (9ae87ae — 20[…]
- Enhanced the Views module with new visual explanations and substantially expanded lesson content. (daf26d0 — 2026-09-12)
- Enhanced the Set Operators module with visual comparisons and substantially expanded lesson content. (b108c42 — 2026-09-02)
- Enhanced the Advanced Aggregations module with lesson navigation, diagrams, and expanded explanations. (d9b0b6b — 2026-09-01)
- Enhanced the String Functions module with lesson navigation, diagrams, and expanded explanations. (33267a1 — 2026-08-27)
- Updated the project author profile and official portfolio information in the README, including the official resource citation. (420f4a9 — 2026-08-30)
Removed
- Removed module status information from the root README to keep progress claims centralized in the roadmap. (db7fad0, ff30e92 — 2026-09-16)
- Removed module badges from the String Functions README to reduce visual clutter. (550821e6 — 2026-09-01)
Fixed
- Corrected and synchronized Resources documentation, links, naming, folder casing, asset references, and library status details while expanding the resource collection. (9ae87ae — 2026-09-12)
- Updated README presentation and contact information to use the current official portfolio URL and Data Analyst title. (420f4a9 — 2026-08-30)
Documentation
- Documented the new Query Optimization module and its supporting local-ignore and CI conventions. (2c510a0 — 2026-09-22)
- Added diagrams and navigation links throughout the Advanced Aggregations, String Functions, Set Operators, and Views modules. (d9b0b6b, 33267a1, b108c42, daf26d0 — 2026-08-27–2026-09-12)
- Expanded the Resources library documentation with 12 resource files, 13 SVG assets, reading roadmaps, quality standards, and contribution guidance. (9ae87ae — 2026-09-12)
[1.1.0] - 2026-07-26
Added
- Advanced Aggregations module with business-case examples and expanded Aggregations content. (Jul 20, 2026)
- Views module. (Jul 15, 2026)
- Set Operators module. (Jul 14, 2026)
- String Functions module and status updated to “Complete”. (Jul 10, 2026)
- NULL Handling and Data Cleaning module. (Jul 11, 2026)
- Complete Date Functions module and module README. (Jul 08, 2026)
- Window Functions materials and business cases:
- Comprehensive Window Functions README and learning objectives. (Jul 03, 2026)
- ROW_NUMBER, RANK, and DENSE_RANK examples and SQL files. (Jul 03–07, 2026)
- PARTITION BY documentation and advanced window-function lessons. (Jul 04, 2026)
- Banking & finance business-case studies for window functions. (Jul 06–07, 2026)
- GitHub Actions workflows and repository infrastructure files (linting, templates). (Jul 08, 2026)
Changed
- Revised README across multiple commits for improved presentation, banners, images, badges, and navigation. (Jun 30 – Jul 23, 2026)
- Reorganized repository structure and module numbering for clarity; renamed files where necessary. (Jul 10–13, 2026)
- DATABASE_SCHEMA.md revised for clarity and improved table descriptions. (Jul 05, 2026)
- ROADMAP.md refined with clearer examples and release planning. (Jul 03, 2026)
Removed
- Deleted obsolete directories and files: Resources (multiple files like Resources/x.md), X-Schema directory, and 09_Business_Case_Studies. (Jul 10–26, 2026)
- Cleaned up branding/assets: removed .DS_Store files and adjusted assets as needed. (Jun 30 – Jul 12, 2026)
Fixed
- Fixed typos and link references (e.g., PARTITON → PARTITION; Module 05 link fix). (Jul 04, Jul 20, 2026)
Documentation
- Added ARCHITECTURE.md and STYLE_GUIDE.md to document repo architecture and standards. (Jul 08, 2026)
- Created SUPPORT.md and FAQ.md to help contributors and users. (Jul 03, 2026)
- Created CHANGELOG.md (initial) and updated it with recent additions. (Jul 03, 2026)
- Added CODEOWNERS, markdownlint config, PR/issue templates, and contributor guidance. (Jul 08, 2026)
[1.0.0] - 2026-07-03
Added
Initial Public Release
Module 1 — Fundamentals
- Core SQL querying fundamentals
- Documentation and SQL examples
Module 2 — Aggregations
- Aggregate functions
- GROUP BY and HAVING
- Practice examples
Module 3 — Joins
- INNER, LEFT, RIGHT, FULL OUTER and CROSS JOIN
- Real-world join scenarios
Module 4 — Subqueries
- Scalar subqueries
- Correlated subqueries
Module 5 — CASE WHEN Statements
- Simple CASE
- Searched CASE
- Business logic implementations
- Conditional aggregations
Module 6 — Common Table Expressions (CTEs)
- Basic CTEs
- Multiple CTEs
- Recursive CTEs
- Advanced CTE patterns
Module 7 — Window Functions
- ROW_NUMBER()
- RANK()
- DENSE_RANK()
- LAG()
- LEAD()
- Running totals
- PARTITION BY
- Window frame specifications
Documentation
- Project README
- Module documentation
- Custom SQL schema
- Learning resources
- Repository navigation
- MIT License
Repository Features
- Engineering-first learning structure
- Production-inspired SQL examples
- Progressive learning roadmap
- Business-oriented practice problems
- Common mistakes and best practices
- Interview-focused explanations
- Modular repository organization
- Consistent documentation standards
Types of Changes
- Added — New features or documentation
- Changed — Improvements to existing content
- Deprecated — Features scheduled for removal
- Removed — Removed functionality
- Fixed — Bug fixes and corrections
- Security — Security-related changes
Contributing
To contribute to this changelog:
- Follow the format above
- Group changes by type (Added, Changed, etc.)
- Link to relevant issues or pull requests when applicable
- Ensure accuracy of dates and version numbers
For more information, see CONTRIBUTING.md.
Support
If you find any errors in the changelog or have suggestions:
- Open an issue on GitHub
- Submit a pull request with corrections
- Reach out via the discussions tab
Your feedback helps us maintain accurate documentation.
Part of the SQL Engineering Handbook