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Data Engineering Path  ·  Data Modelling
GARAGE SYSTEM CASE STUDY

Step 5: SQL Queries & Use Cases (Garage)

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1. Calculate Grand Total Invoice for a Service Booking

Combines labor charges and parts costs into a single invoice receipt:

SELECT b.booking_id, v.plate_number, 
       c.first_name AS customer_name,
       COALESCE(SUM(bp.quantity_used * p.unit_price), 0) AS parts_total,
       150.00 AS flat_labor_rate, -- Labor calculation
       COALESCE(SUM(bp.quantity_used * p.unit_price), 0) + 150.00 AS grand_total
FROM bookings b
JOIN vehicles v ON b.vehicle_id = v.vehicle_id
JOIN customers c ON v.customer_id = c.customer_id
LEFT JOIN booking_parts bp ON b.booking_id = bp.booking_id
LEFT JOIN parts p ON bp.part_id = p.part_id
WHERE b.booking_id = 456
GROUP BY b.booking_id, v.plate_number, c.first_name;

2. Identify Out-of-Stock Parts (Reorder Alert)

SELECT part_name, sku, quantity_in_stock
FROM parts
WHERE quantity_in_stock <= 5;
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