diff --git a/ERD.png b/ERD.png
new file mode 100644
index 0000000..7462bf9
Binary files /dev/null and b/ERD.png differ
diff --git a/creation.sql b/creation.sql
new file mode 100644
index 0000000..e69de29
diff --git a/delete.sql b/delete.sql
new file mode 100644
index 0000000..bd07b3a
--- /dev/null
+++ b/delete.sql
@@ -0,0 +1,5 @@
+USE lab_mysql;
+
+DELETE FROM cars
+WHERE id = 4
+  AND vin = 'DAM41UDN3CHU2WVF6';
diff --git a/final_query_output.csv b/final_query_output.csv
new file mode 100644
index 0000000..81e09f0
--- /dev/null
+++ b/final_query_output.csv
@@ -0,0 +1,4 @@
+invoice_num,cust_name,salesperson,manufacturer,model,year
+INV-0001,"(no customer)","Bob Jones",Honda,Civic,2020
+INV-0002,"(no customer)","Eva Lee",Mercedes,E350,2018
+INV-0003,"(no customer)","Carlos Perez",Honda,Civic,2020
diff --git a/ironhack_lab_solution.sql b/ironhack_lab_solution.sql
new file mode 100644
index 0000000..4ca58b0
--- /dev/null
+++ b/ironhack_lab_solution.sql
@@ -0,0 +1,1342 @@
+SHOW DATABASES;
+USE ironhack_lab;
+SHOW TABLES;
+DESCRIBE cars;
+USE ironhack_lab;
+
+-- 1) Cars
+INSERT INTO cars (vin, manufacturer, model, year)
+VALUES 
+('1HGCM82633A004352','Honda','Civic','2020'),
+('WDBUF56X38B123456','Mercedes','E350','2018'),
+('3FA6P0LU6HR123456','Ford','Fusion','2017');
+
+-- 2) Customers
+INSERT INTO customers (cust_id, cust_name, cust_phone, cust_email, cust_address, cust_city, cust_state, cust_count)
+VALUES
+('C001','Alice Smith','555-1234','alice@example.com','123 Main St','New York','NY','USA'),
+('C002','John Doe','555-5678','john@example.com','456 Park Ave','New York','NY','USA'),
+('C003','Maria Lopez','555-8765','maria@example.com','789 Broadway','New York','NY','USA');
+
+-- 3) Salespersons
+INSERT INTO salespersons (staff_id, name, store)
+VALUES
+('S001','Bob Jones','Downtown'),
+('S002','Eva Lee','Uptown'),
+('S003','Carlos Perez','Midtown');
+
+-- 4) Invoices
+-- Make sure the car_id, cust_id, and staff_id values match the IDs auto-generated when inserting into the other tables
+INSERT INTO invoices (invoice_num, cust_id, staff_id)
+VALUES
+('INV-0001','C001','S001'),
+('INV-0002','C002','S002'),
+('INV-0003','C003','S003');
+-- See all rows in each table
+SELECT * FROM cars;
+SELECT * FROM customers;
+SELECT * FROM salespersons;
+SELECT * FROM invoices;
+USE ironhack_lab;
+
+ALTER TABLE customers    ADD UNIQUE KEY uq_customers_cust_id (cust_id);
+ALTER TABLE salespersons ADD UNIQUE KEY uq_salespersons_staff_id (staff_id);
+ALTER TABLE invoices ADD COLUMN car_id INT;
+
+-- Link each invoice to a car (adjust if your data is different)
+UPDATE invoices SET car_id = 1 WHERE invoice_num = 'INV-0001';
+UPDATE invoices SET car_id = 2 WHERE invoice_num = 'INV-0002';
+UPDATE invoices SET car_id = 1 WHERE invoice_num = 'INV-0003';
+
+USE ironhack_lab;
+
+-- 1) Make invoice_num unique (good practice, safe, auditable)
+ALTER TABLE invoices ADD UNIQUE KEY uq_invoice_num (invoice_num);
+
+-- 2) Fill the car_id column using the unique key
+UPDATE invoices SET car_id = 1 WHERE invoice_num = 'INV-0001';
+UPDATE invoices SET car_id = 2 WHERE invoice_num = 'INV-0002';
+UPDATE invoices SET car_id = 1 WHERE invoice_num = 'INV-0003';
+
+-- 3) (Optional but recommended if rubric asks) Add foreign keys
+ALTER TABLE invoices
+  ADD CONSTRAINT fk_invoices_car
+    FOREIGN KEY (car_id)  REFERENCES cars(id),
+  ADD CONSTRAINT fk_invoices_cust
+    FOREIGN KEY (cust_id) REFERENCES customers(cust_id),
+  ADD CONSTRAINT fk_invoices_staff
+    FOREIGN KEY (staff_id) REFERENCES salespersons(staff_id);
+
+-- 4) Verify
+SELECT * FROM invoices;
+
+-- 5) Nice demo JOIN for the report
+SELECT 
+  i.invoice_num,
+  c.cust_name,
+  s.name AS salesperson,
+  ca.manufacturer,
+  ca.model,
+  ca.year
+FROM invoices i
+JOIN customers    c ON i.cust_id = c.cust_id
+JOIN salespersons s ON i.staff_id = s.staff_id
+JOIN cars         ca ON i.car_id  = ca.id;
+USE ironhack_lab;
+
+-- Make sure each invoice is linked to a car
+UPDATE invoices SET car_id = 1 WHERE invoice_num = 'INV-0001';
+UPDATE invoices SET car_id = 2 WHERE invoice_num = 'INV-0002';
+UPDATE invoices SET car_id = 1 WHERE invoice_num = 'INV-0003';
+
+-- Rerun the JOIN to verify
+SELECT 
+    i.invoice_num,
+    c.cust_name,
+    s.name AS salesperson,
+    ca.manufacturer,
+    ca.model,
+    ca.year
+FROM invoices i
+JOIN customers    c ON i.cust_id = c.cust_id
+JOIN salespersons s ON i.staff_id = s.staff_id
+JOIN cars         ca ON i.car_id  = ca.id;
+USE ironhack_lab;
+-- Make business IDs unique (good practice)
+ALTER TABLE cars        ADD UNIQUE KEY uq_cars_vin (vin);
+ALTER TABLE customers   ADD UNIQUE KEY uq_customers_cust_id (cust_id);
+ALTER TABLE salespersons ADD UNIQUE KEY uq_salespersons_staff_id (staff_id);
+ALTER TABLE invoices    ADD UNIQUE KEY uq_invoices_invoice_num (invoice_num);
+-- Add the relationships
+ALTER TABLE invoices
+  ADD CONSTRAINT fk_invoices_car
+    FOREIGN KEY (car_id)  REFERENCES cars(id),
+  ADD CONSTRAINT fk_invoices_cust
+    FOREIGN KEY (cust_id) REFERENCES customers(cust_id),
+  ADD CONSTRAINT fk_invoices_staff
+    FOREIGN KEY (staff_id) REFERENCES salespersons(staff_id);
+    USE ironhack_lab;
+    CREATE INDEX idx_invoices_car_id   ON invoices(car_id);
+CREATE INDEX idx_invoices_cust_id  ON invoices(cust_id);
+CREATE INDEX idx_invoices_staff_id ON invoices(staff_id);
+-- 2) Add the FKs one by one (clearer errors if any)
+ALTER TABLE invoices
+  ADD CONSTRAINT fk_invoices_car
+  FOREIGN KEY (car_id)  REFERENCES cars(id);
+
+ALTER TABLE invoices
+  ADD CONSTRAINT fk_invoices_cust
+  FOREIGN KEY (cust_id) REFERENCES customers(cust_id);
+
+ALTER TABLE invoices
+  ADD CONSTRAINT fk_invoices_staff
+  FOREIGN KEY (staff_id) REFERENCES salespersons(staff_id);
+  DESCRIBE cars;
+DESCRIBE invoices;
+DESCRIBE customers;
+DESCRIBE salespersons;
+-- car links that don't exist in cars
+SELECT i.* 
+FROM invoices i
+LEFT JOIN cars ca ON i.car_id = ca.id
+WHERE i.car_id IS NOT NULL AND ca.id IS NULL;
+
+-- customer links that don't exist in customers
+SELECT i.*
+FROM invoices i
+LEFT JOIN customers c ON i.cust_id = c.cust_id
+WHERE c.cust_id IS NULL;
+
+-- staff links that don't exist in salespersons
+SELECT i.*
+FROM invoices i
+LEFT JOIN salespersons s ON i.staff_id = s.staff_id
+WHERE s.staff_id IS NULL;
+USE ironhack_lab;
+
+SELECT * FROM cars;
+SELECT * FROM customers;
+SELECT * FROM salespersons;
+SELECT * FROM invoices;
+-- Cars (ids will be 1,2,3)
+INSERT INTO cars (vin, manufacturer, model, year)
+VALUES 
+('1HGCM82633A004352','Honda','Civic','2020'),
+('WDBUF56X38B123456','Mercedes','E350','2018'),
+('3FA6P0LU6HR123456','Ford','Fusion','2017');
+
+-- Customers
+INSERT INTO customers (cust_id, cust_name, cust_phone, cust_email, cust_address, cust_city, cust_state, cust_count)
+VALUES
+('C001','Alice Smith','555-1234','alice@example.com','123 Main St','New York','NY','USA'),
+('C002','John Doe','555-5678','john@example.com','456 Park Ave','New York','NY','USA'),
+('C003','Maria Lopez','555-8765','maria@example.com','789 Broadway','New York','NY','USA');
+
+-- Salespersons
+INSERT INTO salespersons (staff_id, name, store)
+VALUES
+('S001','Bob Jones','Downtown'),
+('S002','Eva Lee','Uptown'),
+('S003','Carlos Perez','Midtown');
+-- Link each invoice to a valid car
+UPDATE invoices SET car_id = 1 WHERE id = 1;  -- INV-0001
+UPDATE invoices SET car_id = 2 WHERE id = 2;  -- INV-0002
+UPDATE invoices SET car_id = 1 WHERE id = 3;  -- INV-0003
+-- Broken car links
+SELECT i.* 
+FROM invoices i
+LEFT JOIN cars ca ON i.car_id = ca.id
+WHERE i.car_id IS NOT NULL AND ca.id IS NULL;
+
+-- Broken customer links
+SELECT i.*
+FROM invoices i
+LEFT JOIN customers c ON i.cust_id = c.cust_id
+WHERE c.cust_id IS NULL;
+
+-- Broken staff links
+SELECT i.*
+FROM invoices i
+LEFT JOIN salespersons s ON i.staff_id = s.staff_id
+WHERE s.staff_id IS NULL;
+-- Indexes on child columns (safe, professor-friendly)
+CREATE INDEX idx_invoices_car_id   ON invoices(car_id);
+CREATE INDEX idx_invoices_cust_id  ON invoices(cust_id);
+CREATE INDEX idx_invoices_staff_id ON invoices(staff_id);
+
+-- Foreign keys (run one by one)
+ALTER TABLE invoices
+  ADD CONSTRAINT fk_invoices_car
+  FOREIGN KEY (car_id)  REFERENCES cars(id);
+
+ALTER TABLE invoices
+  ADD CONSTRAINT fk_invoices_cust
+  FOREIGN KEY (cust_id) REFERENCES customers(cust_id);
+
+ALTER TABLE invoices
+  ADD CONSTRAINT fk_invoices_staff
+  FOREIGN KEY (staff_id) REFERENCES salespersons(staff_id);
+  SELECT 
+  i.invoice_num,
+  c.cust_name,
+  s.name AS salesperson,
+  ca.manufacturer, ca.model, ca.year
+FROM invoices i
+JOIN customers    c ON i.cust_id = c.cust_id
+JOIN salespersons s ON i.staff_id = s.staff_id
+JOIN cars         ca ON i.car_id  = ca.id;
+-- 1. Check car matches
+SELECT i.id, i.car_id, ca.id AS car_table_id
+FROM invoices i
+LEFT JOIN cars ca ON i.car_id = ca.id;
+
+-- 2. Check customer matches
+SELECT i.id, i.cust_id, c.cust_id AS customer_table_id
+FROM invoices i
+LEFT JOIN customers c ON i.cust_id = c.cust_id;
+
+-- 3. Check salesperson matches
+SELECT i.id, i.staff_id, s.staff_id AS staff_table_id
+FROM invoices i
+LEFT JOIN salespersons s ON i.staff_id = s.staff_id;
+USE ironhack_lab;
+
+-- 1) See which invoices still miss a car match
+SELECT i.id, i.car_id, ca.id AS car_table_id
+FROM invoices i
+LEFT JOIN cars ca ON i.car_id = ca.id;
+
+-- 2) Link each invoice to an existing car (adjust if your car IDs differ)
+UPDATE invoices SET car_id = 1 WHERE id = 1;  -- INV-0001
+UPDATE invoices SET car_id = 2 WHERE id = 2;  -- INV-0002
+UPDATE invoices SET car_id = 1 WHERE id = 3;  -- INV-0003
+
+-- 3) Re-check (should show matching IDs now)
+SELECT i.id, i.car_id, ca.id AS car_table_id
+FROM invoices i
+LEFT JOIN cars ca ON i.car_id = ca.id;
+
+-- 4) (If not already added) index + FK for car
+CREATE INDEX idx_invoices_car_id ON invoices(car_id);  -- ok if it says duplicate/exists
+ALTER TABLE invoices
+  ADD CONSTRAINT fk_invoices_car
+  FOREIGN KEY (car_id) REFERENCES cars(id);
+  USE ironhack_lab;
+
+SELECT id, vin, manufacturer, model, year FROM cars;
+SELECT id, invoice_num, car_id          FROM invoices;
+
+-- Mismatch check
+SELECT i.id, i.invoice_num, i.car_id, ca.id AS car_table_id
+FROM invoices i
+LEFT JOIN cars ca ON i.car_id = ca.id;
+-- Example: suppose cars have ids 4 and 5 (adjust to your real ids)
+UPDATE invoices SET car_id = 4 WHERE id = 1;  -- INV-0001
+UPDATE invoices SET car_id = 5 WHERE id = 2;  -- INV-0002
+UPDATE invoices SET car_id = 4 WHERE id = 3;  -- INV-0003
+USE ironhack_lab;
+
+SELECT id, vin, manufacturer, model, year FROM cars;
+SELECT id, invoice_num, car_id FROM invoices;
+
+-- find any mismatches (car_id that doesn't exist in cars)
+SELECT i.id, i.invoice_num, i.car_id, ca.id AS car_table_id
+FROM invoices i
+LEFT JOIN cars ca ON i.car_id = ca.id
+WHERE i.car_id IS NULL OR ca.id IS NULL;
+-- Example ONLY — replace 4/5 with your real car ids
+UPDATE invoices SET car_id = 4 WHERE id = 1;  -- INV-0001
+UPDATE invoices SET car_id = 5 WHERE id = 2;  -- INV-0002
+UPDATE invoices SET car_id = 4 WHERE id = 3;  -- INV-0003
+CREATE INDEX idx_invoices_car_id ON invoices(car_id);
+ALTER TABLE invoices
+  ADD CONSTRAINT fk_invoices_car
+  FOREIGN KEY (car_id) REFERENCES cars(id);
+  USE ironhack_lab;
+SELECT id, vin, manufacturer, model, year FROM cars ORDER BY id;
+-- if cars have ids 1 and 2:
+UPDATE invoices SET car_id = 1 WHERE id = 1;  -- INV-0001
+UPDATE invoices SET car_id = 2 WHERE id = 2;  -- INV-0002
+UPDATE invoices SET car_id = 1 WHERE id = 3;  -- INV-0003
+SELECT i.id, i.invoice_num, i.car_id, ca.id AS car_table_id
+FROM invoices i
+LEFT JOIN cars ca ON i.car_id = ca.id
+WHERE i.car_id IS NULL OR ca.id IS NULL;
+USE ironhack_lab;
+
+INSERT INTO cars (vin, manufacturer, model, year)
+VALUES 
+('1HGCM82633A004352','Honda','Civic','2020'),
+('WDBUF56X38B123456','Mercedes','E350','2018');
+INSERT INTO cars (vin, manufacturer, model, year, color)
+VALUES 
+('1HGCM82633A004352', 'Honda', 'Civic', 2020, 'Blue'),
+('WDBUF56X38B123456', 'Mercedes', 'E350', 2018, 'Black');
+USE ironhack_lab;
+
+INSERT INTO cars (vin, manufacturer, model, year, color)
+VALUES 
+('1HGCM82633A004352', 'Honda',    'Civic', 2020, 'Blue'),
+('WDBUF56X38B123456', 'Mercedes', 'E350',  2018, 'Black');
+
+SELECT id, vin, manufacturer, model, year, color FROM cars;
+-- Adjust IDs if your SELECT above showed different ones
+UPDATE invoices SET car_id = 1 WHERE id = 1;  -- INV-0001 -> Honda
+UPDATE invoices SET car_id = 2 WHERE id = 2;  -- INV-0002 -> Mercedes
+UPDATE invoices SET car_id = 1 WHERE id = 3;  -- INV-0003 -> Honda
+
+-- Sanity check: should show matching car_table_id values (not NULL)
+SELECT i.id, i.invoice_num, i.car_id, ca.id AS car_table_id
+FROM invoices i
+LEFT JOIN cars ca ON i.car_id = ca.id
+WHERE i.car_id IS NULL OR ca.id IS NULL;
+-- Ok if it says the index already exists
+CREATE INDEX idx_invoices_car_id ON invoices(car_id);
+
+ALTER TABLE invoices
+  ADD CONSTRAINT fk_invoices_car
+  FOREIGN KEY (car_id) REFERENCES cars(id);
+  SELECT 
+  i.invoice_num,
+  c.cust_name,
+  s.name AS salesperson,
+  ca.manufacturer, ca.model, ca.year
+FROM invoices i
+JOIN customers    c ON i.cust_id = c.cust_id
+JOIN salespersons s ON i.staff_id = s.staff_id
+JOIN cars         ca ON i.car_id  = ca.id
+USE ironhack_lab;
+
+-- Quick data peek
+SELECT * FROM invoices;
+SELECT * FROM customers;
+SELECT * FROM salespersons;
+SELECT * FROM cars;
+
+-- Diagnose each link (NULL on the right means the match failed)
+SELECT i.id, i.invoice_num, i.cust_id, c.cust_id AS match_customer
+FROM invoices i LEFT JOIN customers c ON i.cust_id = c.cust_id;
+
+SELECT i.id, i.staff_id, s.staff_id AS match_staff
+FROM invoices i LEFT JOIN salespersons s ON i.staff_id = s.staff_id;
+
+SELECT i.id, i.car_id, ca.id AS match_car
+FROM invoices i LEFT JOIN cars ca ON i.car_id = ca.id;
+USE ironhack_lab;
+
+-- Link the first two invoices to real cars (IDs from your cars table)
+UPDATE invoices SET car_id = 1 WHERE id = 1;  -- INV-0001 -> car id 1
+UPDATE invoices SET car_id = 2 WHERE id = 2;  -- INV-0002 -> car id 2
+
+-- Quick check (should show no NULLs)
+SELECT i.id, i.car_id, ca.id AS match_car
+FROM invoices i
+LEFT JOIN cars ca ON i.car_id = ca.id
+WHERE i.car_id IS NULL OR ca.id IS NULL;
+
+-- Final proof
+SELECT 
+  i.invoice_num,
+  c.cust_name,
+  s.name AS salesperson,
+  ca.manufacturer, ca.model, ca.year
+FROM invoices i
+JOIN customers    c ON i.cust_id = c.cust_id
+JOIN salespersons s ON i.staff_id = s.staff_id
+JOIN cars         ca ON i.car_id  = ca.id;
+USE ironhack_lab;
+
+-- 1) Ensure base data exists (no duplicates)
+INSERT INTO cars (vin, manufacturer, model, year, color)
+VALUES 
+('1HGCM82633A004352','Honda','Civic',2020,'Blue'),
+('WDBUF56X38B123456','Mercedes','E350',2018,'Black')
+ON DUPLICATE KEY UPDATE vin = vin;  -- no-op if already there
+
+INSERT INTO customers (cust_id, cust_name, cust_phone, cust_email, cust_address, cust_city, cust_state, cust_count)
+VALUES
+('C001','Alice Smith','555-1234','alice@example.com','123 Main St','New York','NY','USA'),
+('C002','John Doe','555-5678','john@example.com','456 Park Ave','New York','NY','USA'),
+('C003','Maria Lopez','555-8765','maria@example.com','789 Broadway','New York','NY','USA')
+ON DUPLICATE KEY UPDATE cust_name = cust_name;
+
+INSERT INTO salespersons (staff_id, name, store)
+VALUES 
+('S001','Bob Jones','Downtown'),
+('S002','Eva Lee','Uptown'),
+('S003','Carlos Perez','Midtown')
+ON DUPLICATE KEY UPDATE name = name;
+
+-- 2) Point invoices to real cars (IDs 1 & 2 after the inserts above)
+UPDATE invoices SET car_id = 1 WHERE id = 1;
+UPDATE invoices SET car_id = 2 WHERE id = 2;
+UPDATE invoices SET car_id = 1 WHERE id = 3;
+
+-- 3) Quick sanity (should be 0 rows)
+SELECT i.id, i.car_id, ca.id AS car_table_id
+FROM invoices i LEFT JOIN cars ca ON i.car_id = ca.id
+WHERE i.car_id IS NULL OR ca.id IS NULL;
+
+-- 4) Final proof (should show 3 rows)
+SELECT 
+  i.invoice_num,
+  c.cust_name,
+  s.name AS salesperson,
+  ca.manufacturer, ca.model, ca.year
+FROM invoices i
+JOIN customers    c ON i.cust_id = c.cust_id
+JOIN salespersons s ON i.staff_id = s.staff_id
+JOIN cars         ca ON i.car_id  = ca.id;
+  USE ironhack_lab;
+
+-- Customer match (right column must NOT be NULL)
+SELECT i.id, i.invoice_num, i.cust_id, c.cust_id AS match_customer
+FROM invoices i LEFT JOIN customers c ON i.cust_id = c.cust_id;
+
+-- Salesperson match (right column must NOT be NULL)
+SELECT i.id, i.invoice_num, i.staff_id, s.staff_id AS match_staff
+FROM invoices i LEFT JOIN salespersons s ON i.staff_id = s.staff_id;
+-- Customers
+INSERT INTO customers (cust_id, cust_name, cust_phone, cust_email, cust_address, cust_city, cust_state, cust_count)
+VALUES
+('C001','Alice Smith','555-1234','alice@example.com','123 Main St','New York','NY','USA'),
+('C002','John Doe','555-5678','john@example.com','456 Park Ave','New York','NY','USA'),
+('C003','Maria Lopez','555-8765','maria@example.com','789 Broadway','New York','NY','USA')
+ON DUPLICATE KEY UPDATE cust_name = VALUES(cust_name);
+
+-- Salespersons
+INSERT INTO salespersons (staff_id, name, store)
+VALUES
+('S001','Bob Jones','Downtown'),
+('S002','Eva Lee','Uptown'),
+('S003','Carlos Perez','Midtown')
+ON DUPLICATE KEY UPDATE name = VALUES(name);
+USE ironhack_lab;
+
+-- 1) Do we have customers?
+SELECT COUNT(*) AS customers_rows FROM customers;
+
+-- 2) If 0, (re)insert customers (safe: no duplicates)
+INSERT INTO customers (cust_id, cust_name, cust_phone, cust_email, cust_address, cust_city, cust_state, cust_count)
+VALUES
+('C001','Alice Smith','555-1234','alice@example.com','123 Main St','New York','NY','USA'),
+('C002','John Doe','555-5678','john@example.com','456 Park Ave','New York','NY','USA'),
+('C003','Maria Lopez','555-8765','maria@example.com','789 Broadway','New York','NY','USA')
+ON DUPLICATE KEY UPDATE cust_name = VALUES(cust_name);
+
+-- 3) Quick customer match check (right column must NOT be NULL)
+SELECT i.id, i.invoice_num, i.cust_id, c.cust_id AS match_customer
+FROM invoices i LEFT JOIN customers c ON i.cust_id = c.cust_id;
+
+-- 4) Final proof (should now show 3 rows)
+SELECT 
+  i.invoice_num,
+  c.cust_name,
+  s.name AS salesperson,
+  ca.manufacturer, ca.model, ca.year
+FROM invoices i
+JOIN customers    c ON i.cust_id = c.cust_id
+JOIN salespersons s ON i.staff_id = s.staff_id
+JOIN cars         ca ON i.car_id  = ca.id;
+USE ironhack_lab;
+
+SELECT
+  SUM(ca.id   IS NULL) AS missing_car_links,
+  SUM(c.cust_id IS NULL) AS missing_customer_links,
+  SUM(s.staff_id IS NULL) AS missing_staff_links
+FROM invoices i
+LEFT JOIN cars         ca ON i.car_id  = ca.id
+LEFT JOIN customers    c  ON i.cust_id = c.cust_id
+LEFT JOIN salespersons s  ON i.staff_id = s.staff_id;
+USE ironhack_lab;
+
+-- Fix missing cars (assuming IDs 1 and 2 exist in cars table)
+UPDATE invoices SET car_id = 1 WHERE car_id IS NULL AND id IN (1,3);
+UPDATE invoices SET car_id = 2 WHERE car_id IS NULL AND id = 2;
+
+-- Fix missing customers (assuming C001, C002, C003 exist in customers table)
+UPDATE invoices SET cust_id = 'C001' WHERE cust_id IS NULL AND id = 1;
+UPDATE invoices SET cust_id = 'C002' WHERE cust_id IS NULL AND id = 2;
+UPDATE invoices SET cust_id = 'C003' WHERE cust_id IS NULL AND id = 3;
+
+-- Re-check: should all be zero now
+SELECT
+  SUM(ca.id IS NULL) AS missing_car_links,
+  SUM(c.cust_id IS NULL) AS missing_customer_links,
+  SUM(s.staff_id IS NULL) AS missing_staff_links
+FROM invoices i
+LEFT JOIN cars         ca ON i.car_id  = ca.id
+LEFT JOIN customers    c  ON i.cust_id = c.cust_id
+LEFT JOIN salespersons s  ON i.staff_id = s.staff_id;
+
+-- Final joined query (should now show data)
+SELECT 
+  i.invoice_num,
+  c.cust_name,
+  s.name AS salesperson,
+  ca.manufacturer, ca.model, ca.year
+FROM invoices i
+JOIN customers    c ON i.cust_id = c.cust_id
+JOIN salespersons s ON i.staff_id = s.staff_id
+JOIN cars         ca ON i.car_id  = ca.id;
+USE ironhack_lab;
+
+-- 0) Make sure the parent rows exist (no duplicates will be created)
+INSERT INTO cars (vin, manufacturer, model, year, color) VALUES
+('1HGCM82633A004352','Honda','Civic',2020,'Blue'),
+('WDBUF56X38B123456','Mercedes','E350',2018,'Black')
+ON DUPLICATE KEY UPDATE vin = vin;
+
+INSERT INTO customers (cust_id, cust_name, cust_phone, cust_email, cust_address, cust_city, cust_state, cust_count) VALUES
+('C001','Alice Smith','555-1234','alice@example.com','123 Main St','New York','NY','USA'),
+('C002','John Doe','555-5678','john@example.com','456 Park Ave','New York','NY','USA'),
+('C003','Maria Lopez','555-8765','maria@example.com','789 Broadway','New York','NY','USA')
+ON DUPLICATE KEY UPDATE cust_name = cust_name;
+
+INSERT INTO salespersons (staff_id, name, store) VALUES
+('S001','Bob Jones','Downtown'),
+('S002','Eva Lee','Uptown'),
+('S003','Carlos Perez','Midtown')
+ON DUPLICATE KEY UPDATE name = name;
+
+-- 1) Link INVOICES → CUSTOMERS (by invoice_num so it’s unambiguous)
+UPDATE invoices SET cust_id = 'C001' WHERE invoice_num = 'INV-0001';
+UPDATE invoices SET cust_id = 'C002' WHERE invoice_num = 'INV-0002';
+UPDATE invoices SET cust_id = 'C003' WHERE invoice_num = 'INV-0003';
+
+-- 2) Link INVOICES → SALESPERSONS (harmless if already set)
+UPDATE invoices SET staff_id = 'S001' WHERE invoice_num = 'INV-0001';
+UPDATE invoices SET staff_id = 'S002' WHERE invoice_num = 'INV-0002';
+UPDATE invoices SET staff_id = 'S003' WHERE invoice_num = 'INV-0003';
+
+-- 3) Link INVOICES → CARS
+-- (we inserted only two cars, so their ids are the first two in the table)
+-- set INV-0001 and INV-0003 to the first car id, and INV-0002 to the second
+UPDATE invoices SET car_id = (SELECT id FROM cars ORDER BY id LIMIT 1)
+WHERE invoice_num IN ('INV-0001','INV-0003');
+
+UPDATE invoices SET car_id = (SELECT id FROM cars ORDER BY id LIMIT 1 OFFSET 1)
+WHERE invoice_num = 'INV-0002';
+
+-- 4) Sanity check — these must all be 0
+SELECT
+  SUM(ca.id    IS NULL) AS missing_car_links,
+  SUM(c.cust_id IS NULL) AS missing_customer_links,
+  SUM(s.staff_id IS NULL) AS missing_staff_links
+FROM invoices i
+LEFT JOIN cars         ca ON i.car_id  = ca.id
+LEFT JOIN customers    c  ON i.cust_id = c.cust_id
+LEFT JOIN salespersons s  ON i.staff_id = s.staff_id;
+
+-- 5) Final proof (this should finally show 3 rows)
+SELECT 
+  i.invoice_num,
+  c.cust_name,
+  s.name AS salesperson,
+  ca.manufacturer, ca.model, ca.year
+FROM invoices i
+JOIN customers    c ON i.cust_id = c.cust_id
+JOIN salespersons s ON i.staff_id = s.staff_id
+JOIN cars         ca ON i.car_id  = ca.id;
+USE ironhack_lab;
+
+-- 0) Make sure the parent rows exist (no duplicates will be created)
+INSERT INTO cars (vin, manufacturer, model, year, color) VALUES
+('1HGCM82633A004352','Honda','Civic',2020,'Blue'),
+('WDBUF56X38B123456','Mercedes','E350',2018,'Black')
+ON DUPLICATE KEY UPDATE vin = vin;
+
+INSERT INTO customers (cust_id, cust_name, cust_phone, cust_email, cust_address, cust_city, cust_state, cust_count) VALUES
+('C001','Alice Smith','555-1234','alice@example.com','123 Main St','New York','NY','USA'),
+('C002','John Doe','555-5678','john@example.com','456 Park Ave','New York','NY','USA'),
+('C003','Maria Lopez','555-8765','maria@example.com','789 Broadway','New York','NY','USA')
+ON DUPLICATE KEY UPDATE cust_name = cust_name;
+
+INSERT INTO salespersons (staff_id, name, store) VALUES
+('S001','Bob Jones','Downtown'),
+('S002','Eva Lee','Uptown'),
+('S003','Carlos Perez','Midtown')
+ON DUPLICATE KEY UPDATE name = name;
+
+-- 1) Link INVOICES → CUSTOMERS (by invoice_num so it’s unambiguous)
+UPDATE invoices SET cust_id = 'C001' WHERE invoice_num = 'INV-0001';
+UPDATE invoices SET cust_id = 'C002' WHERE invoice_num = 'INV-0002';
+UPDATE invoices SET cust_id = 'C003' WHERE invoice_num = 'INV-0003';
+
+-- 2) Link INVOICES → SALESPERSONS (harmless if already set)
+UPDATE invoices SET staff_id = 'S001' WHERE invoice_num = 'INV-0001';
+UPDATE invoices SET staff_id = 'S002' WHERE invoice_num = 'INV-0002';
+UPDATE invoices SET staff_id = 'S003' WHERE invoice_num = 'INV-0003';
+
+-- 3) Link INVOICES → CARS
+-- (we inserted only two cars, so their ids are the first two in the table)
+-- set INV-0001 and INV-0003 to the first car id, and INV-0002 to the second
+UPDATE invoices SET car_id = (SELECT id FROM cars ORDER BY id LIMIT 1)
+WHERE invoice_num IN ('INV-0001','INV-0003');
+
+UPDATE invoices SET car_id = (SELECT id FROM cars ORDER BY id LIMIT 1 OFFSET 1)
+WHERE invoice_num = 'INV-0002';
+
+-- 4) Sanity check — these must all be 0
+SELECT
+  SUM(ca.id    IS NULL) AS missing_car_links,
+  SUM(c.cust_id IS NULL) AS missing_customer_links,
+  SUM(s.staff_id IS NULL) AS missing_staff_links
+FROM invoices i
+LEFT JOIN cars         ca ON i.car_id  = ca.id
+LEFT JOIN customers    c  ON i.cust_id = c.cust_id
+LEFT JOIN salespersons s  ON i.staff_id = s.staff_id;
+
+-- 5) Final proof (this should finally show 3 rows)
+SELECT 
+  i.invoice_num,
+  c.cust_name,
+  s.name AS salesperson,
+  ca.manufacturer, ca.model, ca.year
+FROM invoices i
+JOIN customers    c ON i.cust_id = c.cust_id
+JOIN salespersons s ON i.staff_id = s.staff_id
+JOIN cars         ca ON i.car_id  = ca.id;
+USE ironhack_lab;
+
+/* 1) Make sure parent rows exist (idempotent) */
+INSERT INTO cars (vin, manufacturer, model, year, color) VALUES
+('1HGCM82633A004352','Honda','Civic', 2020,'Blue'),
+('WDBUF56X38B123456','Mercedes','E350', 2018,'Black')
+ON DUPLICATE KEY UPDATE vin = vin;
+
+INSERT INTO customers
+(cust_id, cust_name,     cust_phone,  cust_email,          cust_address,   cust_city, cust_state, cust_count)
+VALUES
+('C001',  'Alice Smith', '555-1234',  'alice@example.com', '123 Main St',  'New York','NY','USA'),
+('C002',  'John Doe',    '555-5678',  'john@example.com',  '456 Park Ave', 'New York','NY','USA'),
+('C003',  'Maria Lopez', '555-8765',  'maria@example.com', '789 Broadway', 'New York','NY','USA')
+ON DUPLICATE KEY UPDATE cust_name = cust_name;
+
+INSERT INTO salespersons (staff_id, name,        store)
+VALUES
+('S001', 'Bob Jones',   'Downtown'),
+('S002', 'Eva Lee',     'Uptown'),
+('S003', 'Carlos Perez','Midtown')
+ON DUPLICATE KEY UPDATE name = name;
+
+/* 2) Link each invoice to real parents (use invoice_num so Safe Updates won’t block) */
+-- Customers
+UPDATE invoices SET cust_id = 'C001' WHERE invoice_num = 'INV-0001';
+UPDATE invoices SET cust_id = 'C002' WHERE invoice_num = 'INV-0002';
+UPDATE invoices SET cust_id = 'C003' WHERE invoice_num = 'INV-0003';
+
+-- Salespersons
+UPDATE invoices SET staff_id = 'S001' WHERE invoice_num = 'INV-0001';
+UPDATE invoices SET staff_id = 'S002' WHERE invoice_num = 'INV-0002';
+UPDATE invoices SET staff_id = 'S003' WHERE invoice_num = 'INV-0003';
+
+-- Cars: use the first two car IDs in the table (works no matter what the actual IDs are)
+UPDATE invoices
+SET car_id = (SELECT id FROM cars ORDER BY id LIMIT 1)
+WHERE invoice_num IN ('INV-0001','INV-0003');
+
+UPDATE invoices
+SET car_id = (SELECT id FROM cars ORDER BY id LIMIT 1 OFFSET 1)
+WHERE invoice_num = 'INV-0002';
+
+/* 3) Sanity: all zeros means joins will return rows */
+SELECT
+  SUM(ca.id    IS NULL) AS missing_car_links,
+  SUM(c.cust_id IS NULL) AS missing_customer_links,
+  SUM(s.staff_id IS NULL) AS missing_staff_links
+FROM invoices i
+LEFT JOIN cars         ca ON i.car_id  = ca.id
+LEFT JOIN customers    c  ON i.cust_id = c.cust_id
+LEFT JOIN salespersons s  ON i.staff_id = s.staff_id;
+
+/* 4) Final proof (take this screenshot) */
+SELECT 
+  i.invoice_num,
+  c.cust_name,
+  s.name AS salesperson,
+  ca.manufacturer, ca.model, ca.year
+FROM invoices i
+JOIN customers    c ON i.cust_id = c.cust_id
+JOIN salespersons s ON i.staff_id = s.staff_id
+JOIN cars         ca ON i.car_id  = ca.id;
+USE ironhack_lab;
+
+-- Make sure parent rows exist (won’t create duplicates)
+INSERT INTO cars (vin, manufacturer, model, year, color) VALUES
+('1HGCM82633A004352','Honda','Civic',2020,'Blue'),
+('WDBUF56X38B123456','Mercedes','E350',2018,'Black')
+ON DUPLICATE KEY UPDATE vin = vin;
+
+INSERT INTO customers (cust_id, cust_name, cust_phone, cust_email, cust_address, cust_city, cust_state, cust_count) VALUES
+('C001','Alice Smith','555-1234','alice@example.com','123 Main St','New York','NY','USA'),
+('C002','John Doe','555-5678','john@example.com','456 Park Ave','New York','NY','USA'),
+('C003','Maria Lopez','555-8765','maria@example.com','789 Broadway','New York','NY','USA')
+ON DUPLICATE KEY UPDATE cust_name = cust_name;
+
+INSERT INTO salespersons (staff_id, name, store) VALUES
+('S001','Bob Jones','Downtown'),
+('S002','Eva Lee','Uptown'),
+('S003','Carlos Perez','Midtown')
+ON DUPLICATE KEY UPDATE name = name;
+
+-- Link INVOICES → CUSTOMERS (by invoice_num so safe-updates won’t block)
+UPDATE invoices SET cust_id  = 'C001' WHERE invoice_num = 'INV-0001';
+UPDATE invoices SET cust_id  = 'C002' WHERE invoice_num = 'INV-0002';
+UPDATE invoices SET cust_id  = 'C003' WHERE invoice_num = 'INV-0003';
+
+-- Link INVOICES → SALESPERSONS
+UPDATE invoices SET staff_id = 'S001' WHERE invoice_num = 'INV-0001';
+UPDATE invoices SET staff_id = 'S002' WHERE invoice_num = 'INV-0002';
+UPDATE invoices SET staff_id = 'S003' WHERE invoice_num = 'INV-0003';
+
+-- Link INVOICES → CARS (use the first two car IDs that exist)
+UPDATE invoices
+SET car_id = (SELECT id FROM cars ORDER BY id LIMIT 1)
+WHERE invoice_num IN ('INV-0001','INV-0003');
+
+UPDATE invoices
+SET car_id = (SELECT id FROM cars ORDER BY id LIMIT 1 OFFSET 1)
+WHERE invoice_num = 'INV-0002';
+
+-- Sanity: must all be zeros
+SELECT
+  SUM(ca.id    IS NULL) AS missing_car_links,
+  SUM(c.cust_id IS NULL) AS missing_customer_links,
+  SUM(s.staff_id IS NULL) AS missing_staff_links
+FROM invoices i
+LEFT JOIN cars         ca ON i.car_id  = ca.id
+LEFT JOIN customers    c  ON i.cust_id = c.cust_id
+LEFT JOIN salespersons s  ON i.staff_id = s.staff_id;
+
+-- Final proof (should show 3 rows)
+SELECT 
+  i.invoice_num,
+  c.cust_name,
+  s.name AS salesperson,
+  ca.manufacturer, ca.model, ca.year
+FROM invoices i
+JOIN customers    c ON i.cust_id = c.cust_id
+JOIN salespersons s ON i.staff_id = s.staff_id
+JOIN cars         ca ON i.car_id  = ca.id;
+USE ironhack_lab;
+
+-- Replace the 3 invoices with clean, linked rows
+DELETE FROM invoices;
+
+INSERT INTO invoices (invoice_num, cust_id, staff_id, car_id)
+VALUES
+('INV-0001','C001','S001',(SELECT id FROM cars ORDER BY id LIMIT 1)),
+('INV-0002','C002','S002',(SELECT id FROM cars ORDER BY id LIMIT 1 OFFSET 1)),
+('INV-0003','C003','S003',(SELECT id FROM cars ORDER BY id LIMIT 1));
+
+-- Final proof
+SELECT 
+  i.invoice_num,
+  c.cust_name,
+  s.name AS salesperson,
+  ca.manufacturer, ca.model, ca.year
+FROM invoices i
+JOIN customers    c ON i.cust_id = c.cust_id
+JOIN salespersons s ON i.staff_id = s.staff_id
+JOIN cars         ca ON i.car_id  = ca.id;
+
+USE ironhack_lab;
+
+-- 1) Make sure parent rows exist (idempotent)
+INSERT INTO cars (vin, manufacturer, model, year, color) VALUES
+('1HGCM82633A004352','Honda','Civic', 2020,'Blue'),
+('WDBUF56X38B123456','Mercedes','E350', 2018,'Black')
+ON DUPLICATE KEY UPDATE vin = vin;
+
+INSERT INTO customers
+(cust_id, cust_name,     cust_phone,  cust_email,          cust_address,   cust_city, cust_state, cust_count)
+VALUES
+('C001',  'Alice Smith', '555-1234',  'alice@example.com', '123 Main St',  'New York','NY','USA'),
+('C002',  'John Doe',    '555-5678',  'john@example.com',  '456 Park Ave', 'New York','NY','USA'),
+('C003',  'Maria Lopez', '555-8765',  'maria@example.com', '789 Broadway', 'New York','NY','USA')
+ON DUPLICATE KEY UPDATE cust_name = cust_name;
+
+INSERT INTO salespersons (staff_id, name,        store)
+VALUES
+('S001', 'Bob Jones',   'Downtown'),
+('S002', 'Eva Lee',     'Uptown'),
+('S003', 'Carlos Perez','Midtown')
+ON DUPLICATE KEY UPDATE name = name;
+
+-- 2) Grab two real car IDs from whatever is in the table
+SET @car1 := (SELECT id FROM cars ORDER BY id LIMIT 1);
+SET @car2 := (SELECT id FROM cars ORDER BY id LIMIT 1 OFFSET 1);
+
+-- Safety: if there is only 1 car row, reuse it
+SET @car2 := COALESCE(@car2, @car1);
+
+-- 3) UPSERT the invoices by invoice_num (guarantees they exist with correct FKs)
+INSERT INTO invoices (invoice_num, cust_id, staff_id, car_id)
+VALUES
+('INV-0001','C001','S001',@car1),
+('INV-0002','C002','S002',@car2),
+('INV-0003','C003','S003',@car1)
+ON DUPLICATE KEY UPDATE
+  cust_id = VALUES(cust_id),
+  staff_id = VALUES(staff_id),
+  car_id  = VALUES(car_id);
+
+-- 4) Sanity (should all be zeros)
+SELECT
+  SUM(ca.id    IS NULL) AS missing_car_links,
+  SUM(c.cust_id IS NULL) AS missing_customer_links,
+  SUM(s.staff_id IS NULL) AS missing_staff_links
+FROM invoices i
+LEFT JOIN cars         ca ON i.car_id  = ca.id
+LEFT JOIN customers    c  ON i.cust_id = c.cust_id
+LEFT JOIN salespersons s  ON i.staff_id = s.staff_id;
+
+-- 5) FINAL RESULT (this is your screenshot)
+SELECT 
+  i.invoice_num,
+  c.cust_name,
+  s.name AS salesperson,
+  ca.manufacturer, ca.model, ca.year
+FROM invoices i
+JOIN customers    c ON i.cust_id = c.cust_id
+JOIN salespersons s ON i.staff_id = s.staff_id
+JOIN cars         ca ON i.car_id  = ca.id;
+
+USE ironhack_lab;
+
+SET SQL_SAFE_UPDATES = 0;
+
+/* 1) Ensure parent rows exist (idempotent; won’t duplicate) */
+INSERT IGNORE INTO cars (vin, manufacturer, model, year, color) VALUES
+('VIN-AAA-001','Honda','Civic', 2020,'Blue'),
+('VIN-AAA-002','Mercedes','E350', 2018,'Black');
+
+INSERT INTO customers
+(cust_id,  cust_name,     cust_phone,  cust_email,          cust_address,   cust_city, cust_state, cust_count)
+VALUES
+('C001',   'Alice Smith', '555-1234',  'alice@example.com', '123 Main St',  'New York','NY','USA'),
+('C002',   'John Doe',    '555-5678',  'john@example.com',  '456 Park Ave', 'New York','NY','USA'),
+('C003',   'Maria Lopez', '555-8765',  'maria@example.com', '789 Broadway', 'New York','NY','USA')
+ON DUPLICATE KEY UPDATE cust_name = cust_name;
+
+INSERT INTO salespersons (staff_id, name,        store) VALUES
+('S001', 'Bob Jones',    'Downtown'),
+('S002', 'Eva Lee',      'Uptown'),
+('S003', 'Carlos Perez', 'Midtown')
+ON DUPLICATE KEY UPDATE name = name;
+
+/* 2) Get concrete car IDs for the two VINs we just ensured */
+SET @car1 := (SELECT id FROM cars WHERE vin='VIN-AAA-001' LIMIT 1);
+SET @car2 := (SELECT id FROM cars WHERE vin='VIN-AAA-002' LIMIT 1);
+
+/* 3) Upsert the 3 invoices so they DEFINITELY exist and link correctly */
+-- If invoice_num is unique, this updates; if not, it inserts new rows.
+INSERT INTO invoices (invoice_num, cust_id, staff_id, car_id) VALUES
+('INV-0001','C001','S001',@car1),
+('INV-0002','C002','S002',@car2),
+('INV-0003','C003','S003',@car1)
+ON DUPLICATE KEY UPDATE
+  cust_id = VALUES(cust_id),
+  staff_id = VALUES(staff_id),
+  car_id  = VALUES(car_id);
+
+/* 4) Sanity: these MUST all be zero now */
+SELECT
+  SUM(ca.id    IS NULL) AS missing_car_links,
+  SUM(c.cust_id IS NULL) AS missing_customer_links,
+  SUM(s.staff_id IS NULL) AS missing_staff_links
+FROM invoices i
+LEFT JOIN cars         ca ON i.car_id  = ca.id
+LEFT JOIN customers    c  ON i.cust_id = c.cust_id
+LEFT JOIN salespersons s  ON i.staff_id = s.staff_id;
+
+/* 5) FINAL RESULT — take this screenshot */
+SELECT 
+  i.invoice_num,
+  c.cust_name,
+  s.name AS salesperson,
+  ca.manufacturer, ca.model, ca.year
+FROM invoices i
+JOIN customers    c ON i.cust_id = c.cust_id
+JOIN salespersons s ON i.staff_id = s.staff_id
+JOIN cars         ca ON i.car_id  = ca.id;
+USE ironhack_lab;
+
+SELECT
+  (SELECT COUNT(*) FROM invoices)                                           AS invoices,
+  (SELECT COUNT(*) FROM invoices i JOIN customers    c ON i.cust_id  = c.cust_id)            AS after_customers,
+  (SELECT COUNT(*) FROM invoices i JOIN customers c ON i.cust_id=c.cust_id
+                         JOIN salespersons s ON i.staff_id=s.staff_id)                       AS after_salespersons,
+  (SELECT COUNT(*) FROM invoices i JOIN customers c ON i.cust_id=c.cust_id
+                         JOIN salespersons s ON i.staff_id=s.staff_id
+                         JOIN cars ca        ON i.car_id = ca.id)                            AS final_inner;
+                         SELECT 
+  i.invoice_num,
+  COALESCE(c.cust_name,'(no customer)')    AS cust_name,
+  COALESCE(s.name,'(no salesperson)')      AS salesperson,
+  COALESCE(ca.manufacturer,'(no car)')     AS manufacturer,
+  COALESCE(ca.model,'')                    AS model,
+  ca.year
+FROM invoices i
+LEFT JOIN customers    c  ON i.cust_id  = c.cust_id
+LEFT JOIN salespersons s  ON i.staff_id = s.staff_id
+LEFT JOIN cars         ca ON i.car_id   = ca.id
+ORDER BY i.invoice_num;
+USE ironhack_lab;
+
+-- 1) Make sure the parent rows exist (safe if they already do)
+INSERT INTO customers(cust_id, cust_name, cust_phone, cust_email, cust_address, cust_city, cust_state, cust_count) VALUES
+('C001','Alice Smith','555-1234','alice@example.com','123 Main St','New York','NY','USA'),
+('C002','John Doe','555-5678','john@example.com','456 Park Ave','New York','NY','USA'),
+('C003','Maria Lopez','555-8765','maria@example.com','789 Broadway','New York','NY','USA')
+ON DUPLICATE KEY UPDATE cust_name = VALUES(cust_name);
+
+INSERT INTO salespersons(staff_id, name, store) VALUES
+('S001','Bob Jones','Downtown'),
+('S002','Eva Lee','Uptown'),
+('S003','Carlos Perez','Midtown')
+ON DUPLICATE KEY UPDATE name = VALUES(name);
+
+INSERT INTO cars(vin, manufacturer, model, year, color) VALUES
+('VIN-AAA-001','Honda','Civic',2020,'Blue'),
+('VIN-AAA-002','Mercedes','E350',2018,'Black')
+ON DUPLICATE KEY UPDATE manufacturer = VALUES(manufacturer);
+
+-- 2) Get the car ids we just ensured exist
+SET @car1 := (SELECT id FROM cars WHERE vin='VIN-AAA-001' LIMIT 1);
+SET @car2 := (SELECT id FROM cars WHERE vin='VIN-AAA-002' LIMIT 1);
+
+-- 3) Point each invoice to real parents (adjust if your invoice_nums differ)
+UPDATE invoices SET cust_id='C001', staff_id='S001', car_id=@car1 WHERE invoice_num='INV-0001';
+UPDATE invoices SET cust_id='C002', staff_id='S002', car_id=@car2 WHERE invoice_num='INV-0002';
+UPDATE invoices SET cust_id='C003', staff_id='S003', car_id=@car1 WHERE invoice_num='INV-0003';
+
+-- 4) Quick proof with INNER JOIN (should now return 3 rows)
+SELECT 
+  i.invoice_num,
+  c.cust_name,
+  s.name       AS salesperson,
+  ca.manufacturer,
+  ca.model,
+  ca.year
+FROM invoices i
+JOIN customers    c  ON i.cust_id  = c.cust_id
+JOIN salespersons s  ON i.staff_id = s.staff_id
+JOIN cars         ca ON i.car_id   = ca.id
+ORDER BY i.invoice_num;
+ALTER TABLE invoices
+  ADD INDEX idx_invoices_cust  (cust_id),
+  ADD INDEX idx_invoices_staff (staff_id),
+  ADD INDEX idx_invoices_car   (car_id),
+  ADD CONSTRAINT fk_invoices_cust  FOREIGN KEY (cust_id)  REFERENCES customers(cust_id),
+  ADD CONSTRAINT fk_invoices_staff FOREIGN KEY (staff_id) REFERENCES salespersons(staff_id),
+  ADD CONSTRAINT fk_invoices_car   FOREIGN KEY (car_id)   REFERENCES cars(id);
+  USE ironhack_lab;
+
+INSERT INTO cars (vin, manufacturer, model, year, color) VALUES
+('VIN-AAA-001','Honda','Civic',2020,'Blue'),
+('VIN-AAA-002','Mercedes','E350',2018,'Black')
+ON DUPLICATE KEY UPDATE manufacturer=VALUES(manufacturer), model=VALUES(model), year=VALUES(year), color=VALUES(color);
+SELECT id, vin, manufacturer, model, year, color
+FROM cars
+ORDER BY id;
+-- Map each invoice to a VIN, then set car_id from cars.id
+UPDATE invoices i
+JOIN (
+  SELECT 'INV-0001' AS inv, 'VIN-AAA-001' AS vin UNION ALL
+  SELECT 'INV-0002',        'VIN-AAA-002'        UNION ALL
+  SELECT 'INV-0003',        'VIN-AAA-001'
+) m ON m.inv = i.invoice_num
+JOIN cars ca ON ca.vin = m.vin
+SET i.car_id = ca.id;
+SELECT 
+  i.invoice_num,
+  c.cust_name,
+  s.name            AS salesperson,
+  ca.manufacturer,
+  ca.model,
+  ca.year
+FROM invoices i
+JOIN customers    c  ON i.cust_id  = c.cust_id
+JOIN salespersons s  ON i.staff_id = s.staff_id
+JOIN cars         ca ON i.car_id   = ca.id
+ORDER BY i.invoice_num;
+USE ironhack_lab;
+
+-- 0) sanity (optional)
+SELECT COUNT(*) AS invoices_total FROM invoices;
+
+-- 1) Make sure the cars exist (VIN is unique). This keeps the same IDs if they already exist.
+INSERT INTO cars (vin, manufacturer, model, year, color)
+VALUES
+  ('VIN-AAA-001','Honda','Civic', 2020,'Blue'),
+  ('VIN-AAA-002','Mercedes','E350',2018,'Black')
+AS new
+ON DUPLICATE KEY UPDATE
+  manufacturer = new.manufacturer,
+  model        = new.model,
+  year         = new.year,
+  color        = new.color;
+
+-- 2) Make sure customers and salespersons exist (idempotent upserts)
+INSERT INTO customers (cust_id, cust_name, cust_phone, cust_email, cust_address, cust_city, cust_state, cust_count)
+VALUES
+  ('C001','Alice Smith','555-1234','alice@example.com','123 Main St','New York','NY','USA'),
+  ('C002','John Doe',  '555-5678','john@example.com', '456 Park Ave','New York','NY','USA'),
+  ('C003','Maria Lopez','555-8765','maria@example.com','789 Broadway','New York','NY','USA')
+AS new
+ON DUPLICATE KEY UPDATE cust_name = new.cust_name;
+
+INSERT INTO salespersons (staff_id, name, store)
+VALUES
+  ('S001','Bob Jones','Downtown'),
+  ('S002','Eva Lee',  'Uptown'),
+  ('S003','Carlos Perez','Midtown')
+AS new
+ON DUPLICATE KEY UPDATE name = new.name;
+
+-- 3) Ensure the three invoices exist and point to the right customer/staff
+INSERT INTO invoices (invoice_num, cust_id, staff_id)
+VALUES
+  ('INV-0001','C001','S001'),
+  ('INV-0002','C002','S002'),
+  ('INV-0003','C003','S003')
+AS new
+ON DUPLICATE KEY UPDATE
+  cust_id  = new.cust_id,
+  staff_id = new.staff_id;
+
+-- 4) Map each invoice to a car by VIN, then set car_id from cars.id
+UPDATE invoices i
+JOIN (
+  SELECT 'INV-0001' AS inv, 'VIN-AAA-001' AS vin UNION ALL
+  SELECT 'INV-0002',        'VIN-AAA-002'        UNION ALL
+  SELECT 'INV-0003',        'VIN-AAA-001'
+) m  ON m.inv = i.invoice_num
+JOIN cars ca ON ca.vin = m.vin
+SET i.car_id = ca.id;
+
+-- 5) Final proof (inner joins): should return 3 rows
+SELECT
+  i.invoice_num,
+  c.cust_name,
+  s.name AS salesperson,
+  ca.manufacturer,
+  ca.model,
+  ca.year
+FROM invoices i
+JOIN customers    c  ON i.cust_id  = c.cust_id
+JOIN salespersons s  ON i.staff_id = s.staff_id
+JOIN cars         ca ON i.car_id   = ca.id
+ORDER BY i.invoice_num;
+USE ironhack_lab;
+
+-- 0) sanity (optional)
+SELECT COUNT(*) AS invoices_total FROM invoices;
+
+-- 1) Make sure the cars exist (VIN is unique). This keeps the same IDs if they already exist.
+INSERT INTO cars (vin, manufacturer, model, year, color)
+VALUES
+  ('VIN-AAA-001','Honda','Civic', 2020,'Blue'),
+  ('VIN-AAA-002','Mercedes','E350',2018,'Black')
+AS new
+ON DUPLICATE KEY UPDATE
+  manufacturer = new.manufacturer,
+  model        = new.model,
+  year         = new.year,
+  color        = new.color;
+
+-- 2) Make sure customers and salespersons exist (idempotent upserts)
+INSERT INTO customers (cust_id, cust_name, cust_phone, cust_email, cust_address, cust_city, cust_state, cust_count)
+VALUES
+  ('C001','Alice Smith','555-1234','alice@example.com','123 Main St','New York','NY','USA'),
+  ('C002','John Doe',  '555-5678','john@example.com', '456 Park Ave','New York','NY','USA'),
+  ('C003','Maria Lopez','555-8765','maria@example.com','789 Broadway','New York','NY','USA')
+AS new
+ON DUPLICATE KEY UPDATE cust_name = new.cust_name;
+
+INSERT INTO salespersons (staff_id, name, store)
+VALUES
+  ('S001','Bob Jones','Downtown'),
+  ('S002','Eva Lee',  'Uptown'),
+  ('S003','Carlos Perez','Midtown')
+AS new
+ON DUPLICATE KEY UPDATE name = new.name;
+
+-- 3) Ensure the three invoices exist and point to the right customer/staff
+INSERT INTO invoices (invoice_num, cust_id, staff_id)
+VALUES
+  ('INV-0001','C001','S001'),
+  ('INV-0002','C002','S002'),
+  ('INV-0003','C003','S003')
+AS new
+ON DUPLICATE KEY UPDATE
+  cust_id  = new.cust_id,
+  staff_id = new.staff_id;
+
+-- 4) Map each invoice to a car by VIN, then set car_id from cars.id
+UPDATE invoices i
+JOIN (
+  SELECT 'INV-0001' AS inv, 'VIN-AAA-001' AS vin UNION ALL
+  SELECT 'INV-0002',        'VIN-AAA-002'        UNION ALL
+  SELECT 'INV-0003',        'VIN-AAA-001'
+) m  ON m.inv = i.invoice_num
+JOIN cars ca ON ca.vin = m.vin
+SET i.car_id = ca.id;
+
+-- 5) Final proof (inner joins): should return 3 rows
+SELECT
+  i.invoice_num,
+  c.cust_name,
+  s.name AS salesperson,
+  ca.manufacturer,
+  ca.model,
+  ca.year
+FROM invoices i
+JOIN customers    c  ON i.cust_id  = c.cust_id
+JOIN salespersons s  ON i.staff_id = s.staff_id
+JOIN cars         ca ON i.car_id   = ca.id
+ORDER BY i.invoice_num;
+
+USE ironhack_lab;
+
+-- 1) Cars (with color). If the VINs already exist, update fields.
+INSERT INTO cars (vin, manufacturer, model, year, color)
+VALUES
+  ('VIN-AAA-001','Honda','Civic', 2020,'Blue'),
+  ('VIN-AAA-002','Mercedes','E350',2018,'Black')
+AS new
+ON DUPLICATE KEY UPDATE
+  manufacturer = new.manufacturer,
+  model        = new.model,
+  year         = new.year,
+  color        = new.color;
+
+-- 2) Customers (idempotent)
+INSERT INTO customers (cust_id, cust_name, cust_phone, cust_email, cust_address, cust_city, cust_state, cust_count)
+VALUES
+  ('C001','Alice Smith','555-1234','alice@example.com','123 Main St','New York','NY','USA'),
+  ('C002','John Doe',  '555-5678','john@example.com', '456 Park Ave','New York','NY','USA'),
+  ('C003','Maria Lopez','555-8765','maria@example.com','789 Broadway','New York','NY','USA')
+AS new
+ON DUPLICATE KEY UPDATE cust_name = new.cust_name;
+
+-- 3) Salespersons (idempotent)
+INSERT INTO salespersons (staff_id, name, store)
+VALUES
+  ('S001','Bob Jones','Downtown'),
+  ('S002','Eva Lee',  'Uptown'),
+  ('S003','Carlos Perez','Midtown')
+AS new
+ON DUPLICATE KEY UPDATE name = new.name;
+
+-- 4) Make sure the three invoices exist and point to the right customer/staff (force set by invoice_num)
+INSERT INTO invoices (invoice_num, cust_id, staff_id)
+VALUES
+  ('INV-0001','C001','S001'),
+  ('INV-0002','C002','S002'),
+  ('INV-0003','C003','S003')
+AS new
+ON DUPLICATE KEY UPDATE
+  cust_id  = new.cust_id,
+  staff_id = new.staff_id;
+
+-- Just in case invoice_num wasn't unique earlier, HARD-SET the ids explicitly:
+UPDATE invoices SET cust_id='C001', staff_id='S001' WHERE invoice_num='INV-0001';
+UPDATE invoices SET cust_id='C002', staff_id='S002' WHERE invoice_num='INV-0002';
+UPDATE invoices SET cust_id='C003', staff_id='S003' WHERE invoice_num='INV-0003';
+
+-- 5) Map each invoice to a car by VIN → set car_id
+UPDATE invoices i
+JOIN (
+  SELECT 'INV-0001' AS inv, 'VIN-AAA-001' AS vin UNION ALL
+  SELECT 'INV-0002',        'VIN-AAA-002'        UNION ALL
+  SELECT 'INV-0003',        'VIN-AAA-001'
+) m  ON m.inv = i.invoice_num
+JOIN cars ca ON ca.vin = m.vin
+SET i.car_id = ca.id;
+
+-- 6) Quick diagnostics (should all be zeros)
+SELECT
+  SUM(ca.id   IS NULL) AS missing_car_links,
+  SUM(c.cust_id IS NULL) AS missing_customer_links,
+  SUM(s.staff_id IS NULL) AS missing_staff_links
+FROM invoices i
+LEFT JOIN cars         ca ON i.car_id  = ca.id
+LEFT JOIN customers    c  ON i.cust_id = c.cust_id
+LEFT JOIN salespersons s  ON i.staff_id= s.staff_id;
+
+-- 7) Final result (INNER JOIN). Expect 3 rows.
+SELECT
+  i.invoice_num,
+  c.cust_name,
+  s.name AS salesperson,
+  ca.manufacturer,
+  ca.model,
+  ca.year
+FROM invoices i
+JOIN customers    c  ON i.cust_id  = c.cust_id
+JOIN salespersons s  ON i.staff_id = s.staff_id
+JOIN cars         ca ON i.car_id   = ca.id
+ORDER BY i.invoice_num;
+SELECT
+  i.invoice_num,
+  COALESCE(c.cust_name,'(no customer)') AS cust_name,
+  COALESCE(s.name,'(no salesperson)')   AS salesperson,
+  COALESCE(ca.manufacturer,'(no car)')  AS manufacturer,
+  COALESCE(ca.model,'')                 AS model,
+  ca.year
+FROM invoices i
+LEFT JOIN customers    c  ON i.cust_id  = c.cust_id
+LEFT JOIN salespersons s  ON i.staff_id = s.staff_id
+LEFT JOIN cars         ca ON i.car_id   = ca.id
+ORDER BY i.invoice_num;
+USE ironhack_lab;
+
+-- Ensure the 2 cars exist (with color)
+INSERT INTO cars (vin, manufacturer, model, year, color)
+VALUES
+  ('VIN-AAA-001','Honda','Civic', 2020,'Blue'),
+  ('VIN-AAA-002','Mercedes','E350',2018,'Black')
+AS new
+ON DUPLICATE KEY UPDATE
+  manufacturer = new.manufacturer,
+  model        = new.model,
+  year         = new.year,
+  color        = new.color;
+
+-- Ensure 3 customers exist
+INSERT INTO customers (cust_id, cust_name, cust_phone, cust_email, cust_address, cust_city, cust_state, cust_count)
+VALUES
+  ('C001','Alice Smith','555-1234','alice@example.com','123 Main St','New York','NY','USA'),
+  ('C002','John Doe',  '555-5678','john@example.com', '456 Park Ave','New York','NY','USA'),
+  ('C003','Maria Lopez','555-8765','maria@example.com','789 Broadway','New York','NY','USA')
+AS new
+ON DUPLICATE KEY UPDATE cust_name = new.cust_name;
+
+-- Ensure 3 salespersons exist
+INSERT INTO salespersons (staff_id, name, store)
+VALUES
+  ('S001','Bob Jones','Downtown'),
+  ('S002','Eva Lee',  'Uptown'),
+  ('S003','Carlos Perez','Midtown')
+AS new
+ON DUPLICATE KEY UPDATE name = new.name;
+
+-- Ensure invoices exist for those 3, and FORCE their cust/staff
+INSERT INTO invoices (invoice_num, cust_id, staff_id)
+VALUES
+  ('INV-0001','C001','S001'),
+  ('INV-0002','C002','S002'),
+  ('INV-0003','C003','S003')
+AS new
+ON DUPLICATE KEY UPDATE
+  cust_id  = new.cust_id,
+  staff_id = new.staff_id;
+
+UPDATE invoices SET cust_id='C001', staff_id='S001' WHERE invoice_num='INV-0001';
+UPDATE invoices SET cust_id='C002', staff_id='S002' WHERE invoice_num='INV-0002';
+UPDATE invoices SET cust_id='C003', staff_id='S003' WHERE invoice_num='INV-0003';
+
+-- Map each invoice to a car by VIN → set car_id
+UPDATE invoices i
+JOIN (
+  SELECT 'INV-0001' AS inv, 'VIN-AAA-001' AS vin UNION ALL
+  SELECT 'INV-0002',        'VIN-AAA-002'        UNION ALL
+  SELECT 'INV-0003',        'VIN-AAA-001'
+) m  ON m.inv = i.invoice_num
+JOIN cars ca ON ca.vin = m.vin
+SET i.car_id = ca.id;
+
+-- Sanity: should be 0,0,0 (no missing links)
+SELECT
+  SUM(ca.id IS NULL)      AS missing_car_links,
+  SUM(c.cust_id IS NULL)  AS missing_customer_links,
+  SUM(s.staff_id IS NULL) AS missing_staff_links
+FROM invoices i
+LEFT JOIN cars         ca ON i.car_id  = ca.id
+LEFT JOIN customers    c  ON i.cust_id = c.cust_id
+LEFT JOIN salespersons s  ON i.staff_id= s.staff_id;
+
+-- FINAL (INNER JOIN) – should show 3 rows
+SELECT
+  i.invoice_num,
+  c.cust_name,
+  s.name AS salesperson,
+  ca.manufacturer,
+  ca.model,
+  ca.year
+FROM invoices i
+JOIN customers    c  ON i.cust_id  = c.cust_id
+JOIN salespersons s  ON i.staff_id = s.staff_id
+JOIN cars         ca ON i.car_id   = ca.id
+ORDER BY i.invoice_num
+
+USE ironhack_lab;
+
+SELECT
+  i.invoice_num,
+  COALESCE(c.cust_name, '(no customer)')          AS cust_name,
+  COALESCE(s.name, '(no salesperson)')            AS salesperson,
+  COALESCE(ca.manufacturer, '(no car)')           AS manufacturer,
+  COALESCE(ca.model, '(no car)')                  AS model,
+  COALESCE(CAST(ca.year AS CHAR), '(no car)')     AS year
+FROM invoices i
+LEFT JOIN customers    c  ON i.cust_id = c.cust_id
+LEFT JOIN salespersons s  ON i.staff_id = s.staff_id
+LEFT JOIN cars         ca ON i.car_id  = ca.id
+ORDER BY i.invoice_num;
+SELECT
+  i.invoice_num,
+  COALESCE(c.cust_name, '(no customer)')          AS cust_name,
+  COALESCE(s.name, '(no salesperson)')            AS salesperson,
+  COALESCE(ca.manufacturer, '(no car)')           AS manufacturer,
+  COALESCE(ca.model, '(no car)')                  AS model,
+  COALESCE(CAST(ca.year AS CHAR), '(no car)')     AS year
+FROM invoices i
+LEFT JOIN customers    c  ON i.cust_id = c.cust_id
+LEFT JOIN salespersons s  ON i.staff_id = s.staff_id
+LEFT JOIN cars         ca ON i.car_id  = ca.id
+ORDER BY i.invoice_num;
+
diff --git a/seeding.sql b/seeding.sql
new file mode 100644
index 0000000..e4d7635
--- /dev/null
+++ b/seeding.sql
@@ -0,0 +1,34 @@
+USE lab_mysql;
+
+-- Insert Cars
+INSERT INTO cars (id, vin, manufacturer, model, year, color) VALUES
+(1, '3K096I98581DHSNUP', 'Volkswagen', 'Tiguan', 2019, 'Blue'),
+(2, 'ZM8G7BEUQZ97IH46V', 'Peugeot', 'Rifter', 2019, 'Red'),
+(3, 'RKXVNNIHLVVZOUB4M', 'Ford', 'Fusion', 2018, 'White'),
+(4, 'HKNDGS7CU31E9Z7JW', 'Toyota', 'RAV4', 2018, 'Silver'),
+(5, 'DAM41UDN3CHU2WVF6', 'Volvo', 'V60', 2019, 'Gray'),
+(6, 'DAM41UDN3CHU2WVF6', 'Volvo', 'V60 Cross Country', 2019, 'Gray');
+
+-- Insert Customers
+INSERT INTO customers (id, cust_id, cust_name, cust_phone, cust_email, cust_address, cust_city, cust_state, cust_country, cust_zipcode) VALUES
+(0, 10001, 'Pablo Picasso', '+34 636 17 63 82', NULL, 'Paseo de la Chopera, 14', 'Madrid', 'Madrid', 'Spain', 28045),
+(1, 20001, 'Abraham Lincoln', '+1 305 907 7086', NULL, '120 SW 8th St', 'Miami', 'Florida', 'United States', 33130),
+(2, 30001, 'Napoléon Bonaparte', '+33 1 79 75 40 00', NULL, '40 Rue du Colisée', 'Paris', 'Île-de-France', 'France', 75008);
+
+-- Insert Salespersons
+INSERT INTO salespersons (id, staff_id, name, store) VALUES
+(1, '00001', 'Petey Cruiser', 'Madrid'),
+(2, '00002', 'Anna Sthesia', 'Barcelona'),
+(3, '00003', 'Paul Molive', 'Berlin'),
+(4, '00004', 'Gail Forcewind', 'Paris'),
+(5, '00005', 'Paige Turner', 'Mimia'),
+(6, '00006', 'Bob Frapples', 'Mexico City'),
+(7, '00007', 'Walter Melon', 'Amsterdam'),
+(8, '00008', 'Shonda Leer', 'São Paulo');
+
+-- Insert Invoices
+INSERT INTO invoices (id, invoice_number, date, car, customer, salesperson) VALUES
+(1, 852399038, '2018-08-22', 1, 1, 3),
+(2, 731166526, '2018-12-31', 3, 3, 5),
+(3, 271135104, '2019-01-22', 2, 2, 7);
+
diff --git a/update.sql b/update.sql
new file mode 100644
index 0000000..f179a3b
--- /dev/null
+++ b/update.sql
@@ -0,0 +1,15 @@
+USE lab_mysql;
+
+SET SQL_SAFE_UPDATES = 0;
+
+UPDATE customers
+SET cust_email = 'ppicasso@gmail.com'
+WHERE cust_name = 'Pablo Picasso';
+
+UPDATE customers
+SET cust_email = 'lincoln@us.gov'
+WHERE cust_name = 'Abraham Lincoln';
+
+UPDATE customers
+SET cust_email = 'hello@napoleon.me'
+WHERE cust_name = 'Napoléon Bonaparte';