Implement SExI System SQL Scripts

[florianhysenii]

• Defines the EMPLOYEE table using data from hr/employee_index.csv.

• Inserts sample employee records.

• Created create_expenses.sql:

  • Defines the EXPENSE table for storing last night's receipts.
  • Inserts expense data from the finance/receipts_from_last_night files.
  • Includes inline comments to explain the approach and optimizations.

• Created create_invoices.sql:

  • Defines the INVOICE and SUPPLIER tables.
  • Inserts invoice data from the finance/invoices_due files.
  • Assigns supplier IDs (sorted alphabetically) and sets due dates as the last day of the month.

• Created calculate_largest_expensors.sql:

  • Aggregates employee expenses to report those with a total expensed amount over 1000.
  • Joins EMPLOYEE and EXPENSE tables and retrieves manager names via a self-join.

• Created find_manager_cycles.sql:

  • Implements a recursive CTE to detect cycles in the employee-manager relationships.
  • Returns each employee_id along with the detected loop (manager cycle) as a comma-separated list.

• Created generate_supplier_payment_plans.sql:

  • Generates a monthly supplier payment plan using UNNEST and sequence to simulate monthly payments.
  • Calculates payment amounts, outstanding balances, and corresponding payment dates.
  • Avoids a recursive CTE to ensure compatibility with Trino.