Junior engineer interview: query the application data
Build confidence with filters, joins, NULLs and counts on a realistic product database.
Practise each question under time pressure, then explain your assumptions, data grain and edge cases aloud before comparing solutions.
Start interview practice→ 02
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Your exercises
01Return id, customer_id and order_date for paid orders placed on or after 1 September 2026, sorted newest order_date first and id ascending.
Return order id, customer name and order_date for paid app orders, sorted by order id ascending.
Return id and name for customers whose city is missing, sorted by id ascending.
Return category and product_count for every category, sorted alphabetically by category.
Return customer name and paid_order_count for every customer, including zero. Sort by paid_order_count descending, then name alphabetically.