David_Gonzalez_Techshack_candidate

calculate_largest_expensors.sql

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+-- ============================================================
+-- REPORTING LARGEST EXPENSORS
+-- ============================================================
+-- This query identifies employees whose total expenses exceed 1000.
+-- It includes employee details, their manager's details, and their total expensed amount.
+-- Results are ordered by total_expensed_amount in descending order.
+
+SELECT 
+    e.employee_id AS employee_id,  -- Unique identifier for the employee
+    CONCAT(e.first_name, ' ', e.last_name) AS employee_name,  -- Full name of the employee
+    e.manager_id AS manager_id,  -- Unique identifier for the employee's manager
+    CONCAT(m.first_name, ' ', m.last_name) AS manager_name,  -- Full name of the manager
+    SUM(exp.unit_price * exp.quantity) AS total_expensed_amount  -- Total expenses incurred by the employee
+FROM 
+    EMPLOYEE e  -- Main employee table
+LEFT JOIN 
+    EXPENSE exp ON e.employee_id = exp.employee_id  -- Join with the expense table to get expense details
+LEFT JOIN 
+    EMPLOYEE m ON e.manager_id = m.employee_id  -- Self-join to get the manager's details
+GROUP BY 
+    e.employee_id, e.first_name, e.last_name,  -- Group by employee details
+    e.manager_id, m.first_name, m.last_name  -- Group by manager details to ensure aggregation
+HAVING 
+    SUM(exp.unit_price * exp.quantity) > 1000  -- Filter employees with total expenses greater than 1000
+ORDER BY 
+    total_expensed_amount DESC;  -- Order the results in descending order based on total expenses
+
+-- ============================================================
+-- END OF CODE
+-- ============================================================

create_employees.sql

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+-- ============================================================
+-- SETTING UP THE SCHEMA
+-- ============================================================
+-- Ensure you're working within the correct catalog and schema.
+USE memory.default;
+
+-- ============================================================
+-- DATA LOADING IN NORMAL CONDITIONS
+-- ============================================================
+-- Under normal circumstances, the employee data would be loaded directly
+-- from the hr/employee_index.csv file using a supported method. This could
+-- include an ETL process, COPY INTO statement, or specific file-reading mechanisms
+-- supported by the database engine or your ETL pipeline.
+
+-- Example (pseudo-code):
+-- COPY EMPLOYEE FROM 'path/to/hr/employee_index.csv' WITH CSV HEADER;
+
+-- Since this example does not include direct CSV loading,
+-- we will insert the data manually for demonstration purposes.
+
+-- ============================================================
+-- MANUAL DATA INSERTION
+-- ============================================================
+-- Inserting the data manually for demonstration purposes.
+-- Below are the initial records for the EMPLOYEE table.
+
+-- ============================================================
+-- EMPLOYEE TABLE CREATION
+-- ============================================================
+-- The EMPLOYEE table stores information about company employees.
+-- It includes unique identifiers for each employee, their names,
+-- job titles, and the ID of their manager (if applicable).
+-- Create the EMPLOYEE table without primary or foreign key constraints (Trino doesn't support primary keys, foreign keys, or constraints directly)
+
+CREATE TABLE EMPLOYEE (
+    employee_id TINYINT NOT NULL, -- Unique identifier for each employee
+    first_name VARCHAR(50) NOT NULL, -- Employee's first name
+    last_name VARCHAR(50) NOT NULL, -- Employee's last name
+    job_title VARCHAR(50) NOT NULL, -- Employee's job title
+    manager_id TINYINT -- ID of the employee's manager
+);
+
+-- ============================================================
+-- INSERTING DATA INTO EMPLOYEE TABLE
+-- ============================================================
+-- Below are the initial data records for the EMPLOYEE table.
+-- These records represent current employees and their hierarchical relationships.
+
+INSERT INTO EMPLOYEE (employee_id, first_name, last_name, job_title, manager_id)
+VALUES
+    -- CEO of the company, no manager assigned.
+    -- IMPORTANT: CHECK THIS
+    -- If he is the CEO, why does he report to the CFO?? Maybe is NULL, I need to ask (It is solved in part 4)
+    -- Are the Chief's hierarchies well established?
+    (1, 'Ian', 'James', 'CEO', 4),
+
+    -- CSO (Chief Strategy Officer), reports directly to the CEO.
+    (2, 'Umberto', 'Torrielli', 'CSO', 1),
+
+    -- MD EMEA (Managing Director for Europe, Middle East, Africa), reports to CSO.
+    (3, 'Alex', 'Jacobson', 'MD EMEA', 2),
+
+    -- CFO (Chief Financial Officer), reports to CSO.
+    (4, 'Darren', 'Poynton', 'CFO', 2),
+
+    -- MD APAC (Managing Director for Asia-Pacific), reports to CSO.
+    (5, 'Tim', 'Beard', 'MD APAC', 2),
+
+    -- COS (Chief of Staff), reports directly to the CEO.
+    (6, 'Gemma', 'Dodd', 'COS', 1),
+
+    -- CHR (Chief Human Resources), reports to COS.
+    (7, 'Lisa', 'Platten', 'CHR', 6),
+
+    -- GM Activation (General Manager for Activation), reports to CSO.
+    (8, 'Stefano', 'Camisaca', 'GM Activation', 2),
+
+    -- MD NAM (Managing Director for North America), reports to CSO.
+    (9, 'Andrea', 'Ghibaudi', 'MD NAM', 2);
+
+-- ============================================================
+-- IMPLEMENTATION NOTES
+-- ============================================================
+-- 1. NOT NULL constraints are applied to critical columns (employee_id, first_name, last_name, job_title)
+--    to prevent incomplete records.
+-- 2. If you anticipate more than 255 employees, consider changing TINYINT to SMALLINT or INTEGER.
+
+-- ============================================================
+-- VALIDATIONS
+-- ============================================================
+
+-- Verify that the table exists
+SHOW TABLES FROM memory.default;
+
+-- Describe the table to check its columns and constraints
+DESCRIBE memory.default.EMPLOYEE;
+
+-- Query to find invalid manager IDs that are not present in employee_id
+SELECT e.manager_id
+FROM memory.default.EMPLOYEE e
+LEFT JOIN memory.default.EMPLOYEE m ON e.manager_id = m.employee_id
+WHERE e.manager_id IS NOT NULL AND m.employee_id IS NULL;
+
+-- Retrieve all data from the EMPLOYEE table
+SELECT * FROM memory.default.EMPLOYEE
+ORDER BY employee_id;
+
+-- Query employees with their manager details
+SELECT 
+    e.employee_id AS employee_id,
+    CONCAT(e.first_name, ' ', e.last_name) AS employee_name,
+    e.job_title AS job_title,
+    e.manager_id AS manager_id,
+    CONCAT(m.first_name, ' ', m.last_name) AS manager_name
+FROM memory.default.EMPLOYEE e
+LEFT JOIN memory.default.EMPLOYEE m ON e.manager_id = m.employee_id
+ORDER BY e.employee_id;
+
+-- ============================================================
+-- END OF CODE
+-- ============================================================

create_expenses.sql

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+-- ============================================================
+-- EXPENSE TABLE CREATION
+-- ============================================================
+-- The EXPENSE table tracks expenses incurred by employees,
+-- including item prices and quantities.
+
+CREATE TABLE EXPENSE (
+    employee_id TINYINT NOT NULL, -- Unique identifier for the employee incurring the expense
+    unit_price DECIMAL(8, 2), -- Cost per unit
+    quantity TINYINT -- Number of units purchased
+);
+-- ============================================================
+-- INSERTING DATA INTO THE EXPENSE TABLE
+-- ============================================================
+-- Insert expense records into the EXPENSE table.
+
+INSERT INTO EXPENSE (employee_id, unit_price, quantity)
+VALUES
+    -- Alex Jacobson's expenses
+    (3, 6.50, 14), -- Drinks, lots of drinks
+    (3, 11.00, 20), -- More Drinks
+    (3, 22.00, 18), -- So Many Drinks!
+    (3, 13.00, 75), -- I bought everyone in the bar a drink!
+
+    -- Andrea Ghibaudi's expense
+    (9, 300.00, 1), -- Flights from Mexico back to New York
+
+    -- Darren Poynton's expenses
+    (4, 40.00, 9), -- Ubers to get us all home
+
+    -- Umberto Torrielli's expense
+    (2, 17.50, 4); -- I had too much fun and needed something to eat
+
+-- ============================================================
+-- VALIDATIONS
+-- ============================================================
+
+-- Retrieve all data from the EXPENSE table
+SELECT * FROM EXPENSE;
+
+-- Query to find employee IDs in EXPENSE that are not present in EMPLOYEE
+SELECT e.employee_id
+FROM memory.default.EXPENSE e
+LEFT JOIN memory.default.EMPLOYEE emp ON e.employee_id = emp.employee_id
+WHERE emp.employee_id IS NULL;
+
+-- ============================================================
+-- END OF CODE
+-- ============================================================

create_invoices.sql

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+-- ============================================================
+-- SUPPLIER TABLE CREATION
+-- ============================================================
+-- Stores information about suppliers.
+
+CREATE TABLE SUPPLIER (
+    supplier_id TINYINT NOT NULL, -- Unique identifier for each supplier
+    name VARCHAR NOT NULL -- Name of the supplier
+);
+
+-- Insert suppliers into SUPPLIER table
+INSERT INTO SUPPLIER (supplier_id, name)
+VALUES
+    (1, 'Catering Plus'),
+    (2, 'Dave\'s Discos'),
+    (3, 'Entertainment Tonight'),
+    (4, 'Ice Ice Baby'),
+    (5, 'Party Animals');
+
+
+-- ============================================================
+-- INVOICE TABLE CREATION
+-- ============================================================
+-- Stores information about supplier invoices.
+
+CREATE TABLE INVOICE (
+    supplier_id TINYINT NOT NULL, -- Supplier ID (references SUPPLIER)
+    invoice_amount DECIMAL(8, 2), -- Invoice amount
+    due_date DATE -- Due date (last day of the specified month)
+);
+
+-- Insert invoices into INVOICE table
+-- Since the invoices are from a Christmas party, I supposed that it was in December 2024, the "months from now" calculations start there.
+INSERT INTO INVOICE (supplier_id, invoice_amount, due_date)
+VALUES
+    -- Party Animals invoices
+    (5, 6000.00, DATE('2025-03-31')), -- 3 months from December (March 2025)
+
+    -- Catering Plus invoices
+    (1, 2000.00, DATE('2025-02-28')), -- 2 months from December (February 2025)
+    (1, 1500.00, DATE('2025-03-31')), -- 3 months from December (March 2025)
+
+    -- Dave's Discos invoice
+    (2, 500.00, DATE('2025-01-31')), -- 1 month from December (January 2025)
+
+    -- Entertainment Tonight invoice
+    (3, 6000.00, DATE('2025-03-31')), -- 3 months from December (March 2025)
+
+    -- Ice Ice Baby invoice
+    (4, 4000.00, DATE('2025-06-30')); -- 6 months from December (June 2025)
+
+-- ============================================================
+-- VALIDATIONS
+-- ============================================================
+-- Verify that the tables exists
+SELECT * FROM SUPPLIER ORDER BY supplier_id;
+SELECT * FROM INVOICE ORDER BY supplier_id, due_date;
+
+-- Ensure all supplier IDs in INVOICE exist in SUPPLIER
+SELECT i.supplier_id
+FROM INVOICE i
+LEFT JOIN SUPPLIER s ON i.supplier_id = s.supplier_id
+WHERE s.supplier_id IS NULL;
+
+-- ============================================================
+-- END OF CODE
+-- ============================================================

find_manager_cycles.sql

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+-- ============================================================
+-- DETECTING CYCLES IN EMPLOYEE-MANAGER RELATIONSHIPS
+-- ============================================================
+-- Identifies cycles where employees approve each other's expenses.
+
+WITH RECURSIVE ManagerCycle (employee_id, manager_id, cycle) AS (
+    -- Base case: Start with each employee and their direct manager.
+    SELECT 
+        e.employee_id, 
+        e.manager_id,
+        CAST(e.employee_id AS VARCHAR) AS cycle  -- Initialize the cycle with the employee's ID
+    FROM EMPLOYEE e
+    WHERE e.manager_id IS NOT NULL  -- Exclude employees without a manager
+
+    UNION ALL
+
+    -- Recursive case: Traverse the manager hierarchy to detect cycles.
+    SELECT 
+        e.employee_id, 
+        e.manager_id,
+        CONCAT(mc.cycle, ',', CAST(e.employee_id AS VARCHAR)) AS cycle  -- Append employee ID to the cycle
+    FROM EMPLOYEE e
+    JOIN ManagerCycle mc ON e.manager_id = mc.employee_id  -- Follow the management chain
+    WHERE mc.cycle NOT LIKE CONCAT('%', CAST(e.employee_id AS VARCHAR), '%')  -- Prevent infinite loops by checking if the employee is already in the cycle
+)
+
+SELECT 
+    mc.employee_id, 
+    mc.cycle
+FROM ManagerCycle mc
+WHERE mc.employee_id = SPLIT_PART(mc.cycle, ',', 1);  -- Ensure the first employee in the cycle appears in the result
+
+-- ============================================================
+-- END OF CODE
+-- ============================================================

generate_supplier_payment_plans.sql

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+-- ============================================================
+-- GENERATE MONTHLY PAYMENT PLAN FOR SUPPLIERS
+-- ============================================================
+-- This query calculates a monthly payment plan for suppliers,
+-- ensuring payment dates are of type DATE and correspond to the last day of the month.
+
+WITH InvoiceData AS (
+    -- Step 1: Aggregate invoices per supplier
+    -- For each supplier, calculate the total outstanding balance (sum of invoice amounts).
+    -- The result will have one row per supplier with their total balance.
+    SELECT 
+        s.supplier_id,                           -- Unique identifier for the supplier
+        s.name AS supplier_name,                 -- Name of the supplier
+        SUM(i.invoice_amount) AS total_balance  -- Total outstanding balance for the supplier
+    FROM 
+        SUPPLIER s
+    JOIN 
+        INVOICE i ON s.supplier_id = i.supplier_id -- Join to match invoices with their suppliers
+    GROUP BY 
+        s.supplier_id,                           -- Group by supplier ID
+        s.name                                   -- Group by supplier name
+),
+PaymentSchedule AS (
+    -- Step 2: Generate a payment schedule for each supplier
+    -- The schedule splits the total balance into monthly installments,
+    -- ensuring payments are made on the last day of each month.
+    SELECT 
+        id.supplier_id,                          -- Supplier ID
+        id.supplier_name,                        -- Supplier name
+        monthly_index.index AS monthly_index,    -- Payment month index, generated from SEQUENCE
+        CASE 
+            WHEN monthly_index.index * 1500 >= id.total_balance THEN 
+                -- If the cumulative payments reach or exceed the total balance:
+                id.total_balance - (monthly_index.index - 1) * 1500 -- Remaining balance as final payment
+            ELSE 
+                1500.00 -- Standard monthly payment
+        END AS payment_amount,                   -- Amount to be paid for this month
+        GREATEST(id.total_balance - monthly_index.index * 1500, 0) AS balance_outstanding, 
+        -- Calculate the remaining balance after this payment
+        -- Ensure the balance does not go negative using GREATEST.
+
+        DATE_ADD('day', -1, 
+            DATE_ADD('month', monthly_index.index, DATE_TRUNC('month', DATE('2024-12-31')))
+        ) AS payment_date -- Calculate the last day of the payment month
+        -- First, move forward by the number of months specified by monthly_index.
+        -- Then, subtract one day from the first day of the next month to find the last day of the month.
+    FROM 
+        InvoiceData id
+    CROSS JOIN UNNEST(
+        SEQUENCE(1, CAST(CEIL(id.total_balance / 1500) AS BIGINT)) -- Generate a sequence of months needed to pay off the total balance
+    ) AS monthly_index(index) -- Assign the sequence an alias (monthly_index) with a column (index)
+)
+-- Step 3: Output the final payment schedule
+SELECT 
+    supplier_id,                                 -- Supplier ID
+    supplier_name,                               -- Supplier name
+    payment_amount,                              -- Payment amount for the month
+    balance_outstanding,                         -- Remaining balance after this payment
+    payment_date                                 -- Date of the payment (last day of the month)
+FROM 
+    PaymentSchedule
+ORDER BY 
+    supplier_id,                                 -- Sort by supplier ID
+    payment_date;                                -- Then sort by payment date
+
+-- ============================================================
+-- END OF CODE
+-- ============================================================