What changes are you trying to make? (e.g. Adding or removing code, refactoring existing code, adding reports)

This pull request submits the completed work for Assignment 2 of the SQL module. It includes:

• ✅ Section 1: Logical Data Model (ERD) for a bookstore and extended model
• ✅ Section 2: SQL queries using COALESCE, ROW_NUMBER, DENSE_RANK, COUNT, SUBSTR, INSTR, and UNION
• ✅ Section 3: SQL queries for CROSS JOIN, INSERT, DELETE, and UPDATE operations using temporary and permanent tables
• Added and modified assignment2.sql
• Inserted new records and schema changes in farmersmarket.db (for Section 3)

What did you learn from the changes you have made?

• How to normalize data into logical models using ER diagrams
• How to apply string manipulation and window functions in SQL
• How to simulate transactional updates using SQL’s INSERT, DELETE, and UPDATE
• How to use COALESCE to handle NULLs and maintain clean outputs
• How to manage GitHub version control across multiple steps

Was there another approach you were thinking about making? If so, what approach(es) were you thinking of?

For updating current_quantity in Section 3, I explored using RANK() but chose to filter by ORDER BY market_date DESC LIMIT 1 for simplicity and clarity.

Were there any challenges? If so, what issue(s) did you face? How did you overcome it?

• Initially misunderstood original_price as vendor cost instead of a historical price — corrected this after re-reading the schema and verifying use cases
• Faced challenges updating a dynamic column from a subquery — resolved using COALESCE and a filtered UPDATE with EXISTS
• Had to recreate the product_units table after realizing temporary tables aren’t saved in DB Browser

How were these changes tested?

• Ran all queries locally using DB Browser
• Verified results visually in the database and query output
• Ensured PR diff reflects only intended additions
• Saved .db changes and committed them using Git

A reference to a related issue in your repository (if applicable)

N/A

✅ Checklist

• ✅ I confirm that all queries run correctly in DB Browser
• ✅ My ERD diagrams were included and committed correctly
• ✅ I’ve followed the file structure and naming conventions
• ✅ I’ve pushed changes to the correct assignment-two branch
• ✅ This PR contains completed Assignment 2, Sections 1–3