Solved ex.

calculate_largest_expensors.sql

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+WITH 
+employee_expenses AS 
+(
+	SELECT employee_id, unit_price * quantity AS expensed_amount
+	FROM expense
+),
+total_expenses AS
+(
+	SELECT employee_id, SUM(expensed_amount) AS total_expensed_amount 
+	FROM employee_expenses
+	GROUP BY employee_id
+),
+employee_cte
+AS
+(
+	SELECT employee_id, manager_id,  CONCAT(first_name, ' ', last_name) AS employee_name
+	FROM employee
+),
+
+manager_cte
+AS
+(
+	SELECT employee_id AS manager_id, CONCAT(first_name, ' ', last_name) AS manager_name
+	FROM employee
+)
+
+SELECT te.employee_id, e.employee_name,  e.manager_id, m.manager_name, te.total_expensed_amount
+FROM total_expenses AS te
+LEFT JOIN employee_cte AS e 
+ON e.employee_id = te.employee_id
+LEFT JOIN manager_cte AS m 
+ON m.manager_id = e.manager_id
+WHERE total_expensed_amount > 1000;

create_employees.sql

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+-- When interacting with trino, USE the memory.default catalogue.schema.
+USE memory.default;
+
+
+-- load to table using INSERT 
+CREATE TABLE IF NOT EXISTS employee 
+AS
+SELECT * 
+FROM (
+  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) 
+) as t(employee_id, first_name, last_name, job_title, manager_id);
+
+--2. Set the mxployee_id and manager_id columns to the TINYINT data type.
+ALTER TABLE  IF EXISTS  exployee  ALTER COLUMN exployee_id SET DATA TYPE TINYINT;
+ALTER TABLE  IF EXISTS  exployee  ALTER COLUMN manager_id SET DATA TYPE TINYINT;

create_expenses.sql

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+CREATE TABLE IF NOT EXISTS expense 
+(
+	employee_id TINYINT,
+	unit_price DECIMAL(8, 2),
+	quantity TINYINT
+);
+
+CREATE OR REPLACE VIEW recipes_cleaned AS
+	WITH 
+	receipts_from_last_night
+	AS
+	(
+		SELECT * 
+		FROM ( 
+		  VALUES 
+			   ('Employee: Alex Jacobson', 'Items: Drinks, lots of drinks', 'Unit Price: 6.50', 'Quantity: 14'), -- drinkies.txt
+			   ('Employee: Alex Jacobson', 'Items: More Drinks', 'Unit Price: 11.00', 'Quantity: 20'), -- drinks.txt
+			   ('Employee: Alex Jacobson', 'Items: So Many Drinks!', 'Unit Price: 22.00', 'Quantity: 18'), -- drinkss.txt
+			   ('Employee: Alex Jacobson', 'Items: I bought everyone in the bar a drink!', 'Unit Price: 13.00', 'Quantity: 75'), -- duh_i_think_i_got_too_many.txt
+			   ('Employee: Andrea Ghibaudi', 'Items: Flights from Mexico back to New York', 'Unit Price: 300', 'Quantity: 1'), -- i_got_lost_on_the_way_home_and_now_im_in_mexico.txt
+			   ('Employee: Darren Poynton', 'Items: Ubers to get us all home', 'Unit Price: 40.00', 'Quantity: 9'), -- ubers.txt
+			   ('Employee: Umberto Torrielli', 'Items: I had too much fun and needed something to eat', 'Unit Price: 17.50', 'Quantity: 4') -- we_stopped_for_a_kebabs.txt
+		) AS t(employee, items, unit_price, quantity)
+
+	),
+
+	receipts_from_last_night_cleaned AS (
+		SELECT 
+			split(employee, ': ')[2] AS employee,
+			CAST(split(unit_price, ': ')[2] AS DECIMAL(8,2)) AS unit_price,
+			CAST(split(quantity, ': ')[2] AS TINYINT) AS quantity
+		FROM receipts_from_last_night
+	)
+	SELECT e.employee_id, r.unit_price, r.quantity
+	FROM receipts_from_last_night_cleaned AS r
+	LEFT JOIN employee AS e
+		ON r.employee = e.first_name || ' ' || e.last_name;
+
+INSERT INTO expense (employee_id, unit_price, quantity)
+SELECT employee_id, unit_price, quantity 
+FROM recipes_cleaned;

create_invoices.sql

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+
+CREATE TABLE IF NOT EXISTS invoice
+(
+	supplier_id TINYINT,
+	invoice_amount DECIMAL(8, 2),
+	due_date DATE
+);
+
+CREATE TABLE IF NOT EXISTS supplier
+(
+	supplier_id TINYINT,
+	supplier_name VARCHAR
+);
+
+
+CREATE OR REPLACE VIEW invoices_cleaned 
+AS 
+	WITH  
+	invoices_due
+	AS 
+	(SELECT * 
+		FROM ( 
+		  VALUES 
+			('Invoice', '-------','Company Name: Party Animals', 'Invoice Items: Zebra, Lion, Giraffe, Hippo', 'Invoice Amount: 6000', 'Due Date: 3 months from now'), -- awesome_animals.txt
+			('Invoice', '-------', 'Company Name: Catering Plus',  'Invoice Items: Champagne, Whiskey, Vodka, Gin, Rum, Beer, Wine.','Invoice Amount: 2000','Due Date: 2 months from now'), -- brilliant_bottles.txt
+			('Invoice', '-------', 'Company Name: Catering Plus', 'Invoice Items: Pizzas, Burgers, Hotdogs, Cauliflour Wings, Caviar', 'Invoice Amount: 1500','Due Date: 3 months from now'), -- crazy_catering.txt
+			('Invoice', '-------', 'Company Name: Dave''s Discos', 'Invoice Items: Dave, Dave Equipment', 'Invoice Amount: 500', 'Due Date: 1 month from now'), -- disco_dj.txt
+			('Invoice', '-------', 'Company Name: Entertainment tonight', 'Invoice Items: Portable Lazer tag, go carts, virtual darts, virtual shooting, puppies.', 'Invoice Amount: 6000',  'Due Date: 3 months from now'), -- excellent_entertainment.txt
+			('Invoice', '-------', 'Company Name: Ice Ice Baby', 'Invoice Items: Ice Luge, Lifesize ice sculpture of Umberto',  'Invoice Amount: 4000',  'Due Date: 6 months from now')
+		) as t(header_part_1, header_part_2, company_name, invoice_items,invoice_amount_raw,  due_date_raw )
+	),
+	invoices_due_cleaned AS 
+	(
+	   SELECT SPLIT(company_name, ': ')[2] AS supplier_name, 
+			  CAST(SPLIT(invoice_amount_raw, ': ')[2] AS DECIMAL(8, 2))  AS invoice_amount,  
+			  current_date + CAST(regexp_extract(due_date_raw,  '([0-9]+)', 1) AS INTEGER) * INTERVAL '1' MONTH  AS  due_date_raw
+	   FROM invoices_due
+	),
+
+	suppliers_raw AS 
+	(
+		SELECT DISTINCT supplier_name 
+		FROM invoices_due_cleaned
+	),
+
+	suppliers AS
+	(
+		SELECT ROW_NUMBER() OVER (ORDER BY supplier_name ASC) AS supplier_id,  supplier_name
+		FROM suppliers_raw
+	)
+
+	SELECT s.supplier_id,
+	       s.supplier_name,
+		   invoice_amount,
+		   date_trunc('month' ,due_date_raw) + interval '1' MONTH - INTERVAL '1' DAY AS due_date
+	FROM invoices_due_cleaned AS i
+	LEFT JOIN suppliers AS s 
+	ON s.supplier_name = i.supplier_name;
+
+TRUNCATE TABLE invoice; 
+INSERT INTO invoice
+SELECT supplier_id, invoice_amount, due_date
+FROM invoices_cleaned;
+
+TRUNCATE TABLE supplier;
+INSERT INTO supplier
+SELECT DISTINCT supplier_id, supplier_name
+FROM invoices_cleaned;

find_manager_cycles.sql

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+WITH RECURSIVE hierarchy(employee_id, manager_id, path) AS (
+    -- Start with each employee
+    SELECT 
+        e.employee_id,
+        e.manager_id,
+        ARRAY[e.employee_id] AS path
+    FROM employee e
+
+    UNION ALL
+
+    -- Walk upward in the manager chain
+    SELECT 
+        h.employee_id,
+        e.manager_id,
+        h.path || e.employee_id
+    FROM hierarchy h
+    JOIN employee e 
+      ON h.manager_id = e.employee_id
+    -- Prevent infinite loops: stop if employee already visited
+    WHERE NOT contains(h.path, e.employee_id)
+),
+
+
+-- A cycle exists when manager_id points back into the path
+cycles (employee_id,  path) AS (
+    SELECT 
+        employee_id,
+        path
+    FROM hierarchy
+    WHERE CONTAINS(path, manager_id) 
+)
+SELECT 
+    employee_id,
+    array_join(path, ' -> ') AS loop_path
+FROM cycles;

generate_supplier_payment_plans.sql

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+WITH 
+payment_amount AS
+(
+	SELECT supplier_id, due_date AS payment_date, SUM(invoice_amount) AS payment_amount 
+    FROM invoice
+    GROUP BY supplier_id, due_date
+)
+SELECT pa.supplier_id, s.supplier_name, pa.payment_amount, 
+       SUM(pa.payment_amount) OVER (PARTITION BY pa.supplier_id ORDER BY payment_date DESC) AS balance_outstanding,
+       pa.payment_date
+FROM payment_amount AS pa
+LEFT JOIN supplier AS s 
+ON pa.supplier_id = s.supplier_id
+ORDER BY pa.supplier_id ASC ,payment_date ASC;