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
- Expanded Window Business Cases module with additional chapters and diagrams (HR Analytics chapter and visual assets). (e015ecc — 2026-08-12)
- Expanded NULL Handling & Data Cleaning module with visual explanation of three-valued logic and validation guidance. (aed8596 — 2026-08-11)
- Substantially expanded the CTEs module with engineering patterns, diagrams, runnable examples and interview tips. (ffe7ff2 — 2026-08-06)
- Added CASE_WHEN sample schema and seed data (shared schema used across lessons). (4de05c6 — 2026-08-07)
- Added/expanded Aggregations content and assets (new banner image, analytics patterns and examples). (5c11c6a, 88a9ef — 2026-08-07–08)
- Expanded Window Functions lessons (ROW_NUMBER, navigation improvements, diagrams). (24b8a9e — 2026-08-08)
- Resource library: improved Resources/README table and links to curated files (books, certifications, communities, tools). (6ef3561, f346550 — 2026-08-06)
- Added several module assets and diagrams to support lessons (CTE flow, row-number diagrams, HR leaderboard visuals). (ffe7ff2, 24b8a9e, e015ecc — Aug 6–12, 2026)
Changed
- Multiple README updates across the repo: added live GH Pages link, adjusted banners, badges, and navigation for improved presentation and module discoverability. (fcd6556, 259918a, fd0ca21, f346550 — 2026-08-06–11)
- Replaced SVG banner for Aggregations with PNG and updated module README references. (c9ab3ca, 1fc3d69 — 2026-08-07–08)
- Standardized some module README headings and corrected internal links/navigation (various README edits to align module naming and paths). (7679a2d, 9436e62, 56dc371 — 2026-08-06–10)
- Updated .gitignore to include common macOS artifacts (.DS_Store) and minor housekeeping changes. (5c11c6a — 2026-08-07)
Removed
- Removed or simplified some decorative badges and redundant README snippets to reduce clutter and improve readability. (4a3f4a0, fd0ca21 — 2026-08-06)
- Clean-up of temporary/legacy file references in Resources and module READMEs (small pruning across commits). (f346550, 6ef3561 — 2026-08-06)
Fixed
- README formatting and avatar/style adjustments (rounding/corrected attributes) and other small presentation fixes. (c83ff6b, c99c601, fb92943 — 2026-08-07–08)
- Corrected module file references and naming inconsistencies introduced during expansion (e.g., module link paths, consistent module folder names). (7679a2d, 4de05c6 — 2026-08-07–10)
- Incorporated minor query / example corrections that surfaced while expanding lessons (small fixes within lesson files). (multiple commits Aug 6–12, 2026)
Documentation
- Added 00_Sample_Schema.sql (shared sample schema + seed data) to support hands-on lessons and reproducible examples. (4de05c6 — 2026-08-07)
- Added diagrams and assets referenced by new lessons (CTE flow diagrams, ROW_NUMBER visuals, HR leaderboard). (ffe7ff2, 24b8a9e, e015ecc — Aug 6–12, 2026)
- Updated Resources/README to include a structured table of resource files (books, certifications, communities, tools). (6ef3561, f346550 — 2026-08-06)
- Continued README and handbook navigation refinements to make module progression clearer for learners and contributors. (fcd6556, 259918a — 2026-08-06–11)
[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