SQL and Data Modeling
Assesses applied SQL and relational modeling in PostgreSQL: joins, aggregations, NULL, indexes, transactions and schema design. Suited for developers, data analysts and data engineers.
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As the candidate sees it
SQL and Data Modeling
- 1.Short text
Which window expression numbers each customer's orders from newest to oldest?
You want only the latest order of each customer from the table orders(id, customer_id, created_at, amount), then filter on row number 1. Answer with the window function expression you would use in the SELECT.
- 2.Long text
How would you model appointment booking so overlapping slots are impossible?
A clinic chain needs a PostgreSQL database for bookings: locations, practitioners (who work at more than one location), patients, and appointments with start and end times. A practitioner can never have two overlapping appointments, even when two receptionists book at the same time. Canceled appointments must stay in the history. Describe the main tables, keys, constraints and indexes, and explain how the database enforces the no-overlap rule.
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6 more questions in the full template.
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Which window expression numbers each customer's orders from newest to oldest?
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