Implement SExI System SQL Scripts

calculate_largest_expensors.sql

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+USE memory.default;
+
+-- This query reports employees whose total expensed_amount exceeds 1000.
+-- The expensed_amount is computed as unit_price * quantity for each expense.
+-- We join the EXPENSE and EMPLOYEE tables and also fetch the manager's name via a self-join.
+SELECT
+  e.employee_id,
+  CONCAT(e.first_name, ' ', e.last_name) AS employee_name,
+  e.manager_id,
+  CONCAT(m.first_name, ' ', m.last_name) AS manager_name,
+  SUM(exp.unit_price * exp.quantity) AS total_expensed_amount
+FROM EXPENSE exp
+JOIN EMPLOYEE e ON exp.employee_id = e.employee_id
+LEFT JOIN EMPLOYEE m ON e.manager_id = m.employee_id
+GROUP BY 
+  e.employee_id, e.first_name, e.last_name, e.manager_id, m.first_name, m.last_name
+HAVING SUM(exp.unit_price * exp.quantity) > 1000
+ORDER BY total_expensed_amount DESC;
+
+-- Comment: This query aggregates all expenses per employee and filters out those who expensed more than 1000.

create_employees.sql

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+USE memory.default;
+
+-- Creating EMPLOYEE table using data from hr/employee_index.csv file
+CREATE TABLE EMPLOYEE (
+  employee_id TINYINT, 
+  first_name VARCHAR, 
+  last_name VARCHAR, 
+  job_title VARCHAR, 
+  manager_id TINYINT
+)
+COMMENT 'Employee table using data from hr/employee_index.csv file';
+
+-- Inserting data into EMPLOYEE table
+INSERT INTO EMPLOYEE VALUES
+  (1, 'Ian', 'James', 'CEO', 4),
+  (2, 'Umberto', 'Torrielli', 'CSO', 1),
+  (3, 'Alex', 'Jacobson', 'MD EMEA', 2),
+  (4, 'Darren', 'Poynton', 'CFO', 2),
+  (5, 'Tim', 'Beard', 'MD APAC', 2),
+  (6, 'Gemma', 'Dodd', 'COS', 1),
+  (7, 'Lisa', 'Platten', 'CHR', 6),
+  (8, 'Stefano', 'Camisaca', 'GM Activation', 2),
+  (9, 'Andrea', 'Ghibaudi', 'MD NAM', 2);
+
+-- Comment: Data inserted as per employee_index.csv.

create_expenses.sql

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+USE memory.default;
+
+-- Creating EXPENSE table to store last night's receipts.
+CREATE TABLE EXPENSE (
+  employee_id TINYINT,
+  unit_price DECIMAL(8,2),
+  quantity TINYINT
+)
+COMMENT 'Expense table loaded from finance/receipts_from_last_night files';
+
+-- Inserting receipt data from finance/receipts_from_last_night
+
+-- From drinkies.txt:
+-- Employee: Alex Jacobson (employee_id: 3), Unit Price: 6.50, Quantity: 14
+INSERT INTO EXPENSE VALUES (3, 6.50, 14);
+
+-- From drinks.txt:
+-- Employee: Alex Jacobson (employee_id: 3), Unit Price: 11.00, Quantity: 20
+INSERT INTO EXPENSE VALUES (3, 11.00, 20);
+
+-- From drinkss.txt:
+-- Employee: Alex Jacobson (employee_id: 3), record incomplete (no unit price/quantity provided).
+-- We set unit_price and quantity to 0 to indicate missing data.
+INSERT INTO EXPENSE VALUES (3, 0.00, 0);
+
+-- From duh_i_think_i_got_too_many.txt:
+-- Employee: Alex Jacobson (employee_id: 3), Unit Price: 13.00, Quantity: 75
+INSERT INTO EXPENSE VALUES (3, 13.00, 75);
+
+-- From i_got_lost_on_the_way_home_and_now_im_in_mexico.txt:
+-- Employee: Andrea Ghibaudi (employee_id: 9), Unit Price: 300, Quantity: 1
+INSERT INTO EXPENSE VALUES (9, 300.00, 1);
+
+-- From ubers.txt:
+-- Employee: Darren Poynton (employee_id: 4), Unit Price: 40.00, Quantity: 9
+INSERT INTO EXPENSE VALUES (4, 40.00, 9);
+
+-- From we_stopped_for_a_kebabs.txt:
+-- Employee: Umberto Torrielli (employee_id: 2), Unit Price: 17.50, Quantity: 4
+INSERT INTO EXPENSE VALUES (2, 17.50, 4);
+
+-- Comment: Using direct inserts to simulate the imported receipts from text files.

create_invoices.sql

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+USE memory.default;
+
+-- Creating the INVOICE table to store supplier invoice details.
+CREATE TABLE INVOICE (
+  supplier_id TINYINT,
+  invoice_ammount DECIMAL(8,2),
+  due_date DATE
+)
+COMMENT 'Invoice table loaded from finance/invoices_due files';
+
+-- Creating the SUPPLIER table to store supplier details.
+CREATE TABLE SUPPLIER (
+  supplier_id TINYINT,
+  name VARCHAR
+)
+COMMENT 'Supplier table derived from invoice file company names';
+
+-- Inserting supplier data.
+-- Suppliers sorted alphabetically:
+-- 1: Catering Plus
+-- 2: Dave''s Discos
+-- 3: Entertainment tonight
+-- 4: Ice Ice Baby
+-- 5: Party Animals
+
+INSERT INTO SUPPLIER VALUES
+  (1, 'Catering Plus'),
+  (2, 'Dave''s Discos'),
+  (3, 'Entertainment tonight'),
+  (4, 'Ice Ice Baby'),
+  (5, 'Party Animals');
+
+-- Inserting invoice data from invoice files:
+-- awesome_animals.txt:
+--   Company Name: Party Animals, Invoice Amount: 6000, Due Date: 3 months from now (assume 2025-07-31)
+INSERT INTO INVOICE VALUES (5, 6000.00, DATE '2025-07-31');
+
+-- brilliant_bottles.txt:
+--   Company Name: Catering Plus, Invoice Amount: 2000, Due Date: 2 months from now (assume 2025-06-30)
+INSERT INTO INVOICE VALUES (1, 2000.00, DATE '2025-06-30');
+
+-- crazy_catering.txt:
+--   Company Name: Catering Plus, Invoice Amount: 1500, Due Date: 3 months from now (assume 2025-07-31)
+INSERT INTO INVOICE VALUES (1, 1500.00, DATE '2025-07-31');
+
+-- disco_dj.txt:
+--   Company Name: Dave's Discos, Invoice Amount: 500, Due Date: 1 month from now (assume 2025-05-31)
+INSERT INTO INVOICE VALUES (2, 500.00, DATE '2025-05-31');
+
+-- excellent_entertainment.txt:
+--   Company Name: Entertainment tonight, Invoice Amount: 6000, Due Date: 3 months from now (assume 2025-07-31)
+INSERT INTO INVOICE VALUES (3, 6000.00, DATE '2025-07-31');
+
+-- fantastic_ice_sculptures.txt:
+--   Company Name: Ice Ice Baby, Invoice Amount: 4000, Due Date: 6 months from now (assume 2025-10-31)
+INSERT INTO INVOICE VALUES (4, 4000.00, DATE '2025-10-31');
+
+-- Comment: Due dates set to the last day of the respective month based on "n months from now".

find_manager_cycles.sql

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+USE memory.default;
+
+-- This query attempts to detect cycles in the manager relationships (i.e., employees approving each other's expenses).
+-- We use a recursive Common Table Expression (CTE) to build paths from each employee up the management chain.
+-- The resulting path is returned as a comma-separated list of employee_ids indicating the cycle.
+WITH RECURSIVE manager_paths(employee_id, manager_id, path) AS (
+  -- Base step: start with each employee
+  SELECT 
+    employee_id,
+    manager_id,
+    CAST(employee_id AS VARCHAR) AS path
+  FROM EMPLOYEE
+  UNION ALL
+  -- Recursive step: join with EMPLOYEE to follow the manager chain
+  SELECT 
+    mp.employee_id,
+    e.manager_id,
+    CONCAT(mp.path, ',', CAST(e.manager_id AS VARCHAR))
+  FROM manager_paths mp
+  JOIN EMPLOYEE e ON mp.manager_id = e.employee_id
+  -- Prevent cycles from repeating nodes in the path
+  WHERE strpos(mp.path, CAST(e.manager_id AS VARCHAR)) = 0
+)
+-- Select paths where the cycle is closed; for instance, where the current manager_id appears in the path.
+SELECT 
+  employee_id,
+  path AS manager_cycle
+FROM manager_paths
+WHERE strpos(path, CAST(manager_id AS VARCHAR)) > 0;
+
+-- Comment: This recursive CTE builds the chain and then filters for cycles.

generate_supplier_payment_plans.sql

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+USE memory.default;
+
+-- Generate a monthly supplier payment plan.
+-- For each supplier, we assume a fixed maximum monthly payment of 1500.
+-- The total number of payments is calculated as CEIL(total_outstanding / 1500).
+-- Payment dates are generated by adding an offset in months to the end-of-current-month date.
+-- This approach uses UNNEST and sequence() to simulate the recurrence without a recursive CTE.
+
+WITH supplier_totals AS (
+    -- Calculate total outstanding per supplier from all invoices
+    SELECT 
+      s.supplier_id, 
+      s.name AS supplier_name, 
+      SUM(i.invoice_ammount) AS total_outstanding
+    FROM SUPPLIER s
+    JOIN INVOICE i ON s.supplier_id = i.supplier_id
+    GROUP BY s.supplier_id, s.name
+),
+supplier_payments AS (
+    SELECT
+      supplier_id,
+      supplier_name,
+      total_outstanding,
+      CAST(CEIL(total_outstanding / 1500.0) AS INTEGER) AS num_payments
+    FROM supplier_totals
+)
+SELECT 
+    sp.supplier_id,
+    sp.supplier_name,
+    -- Determine payment amount: For all but the last payment, it's 1500, otherwise the remaining balance.
+    CASE 
+      WHEN month_offset < sp.num_payments - 1 THEN 1500.00
+      ELSE sp.total_outstanding - 1500.00 * (sp.num_payments - 1)
+    END AS payment_amount,
+    -- Calculate the remaining balance after the payment at this step
+    sp.total_outstanding - 1500.00 * month_offset AS balance_outstanding,
+    -- Payment date: start at the end of the current month and add month_offset months
+    CAST(date_add('month', month_offset, 
+         CAST(date_trunc('month', CURRENT_DATE) + interval '1' month - interval '1' day AS DATE))
+    AS DATE) AS payment_date
+FROM supplier_payments sp,
+     -- Generate a series [0, num_payments-1] per supplier to represent each payment.
+     UNNEST(sequence(0, sp.num_payments - 1)) AS t(month_offset)
+ORDER BY sp.supplier_id, payment_date;