Question library
Questions from real interviews. Drill any of them by voice in a couple of minutes, with an interviewer, a score and feedback.
What are a primary key and a foreign key? And how would you model a many-to-many relationship, for example students and courses?JuniorWhat are slowly changing dimensions, SCDs, and what types do you know?JuniorWhat is a star schema, and how does it differ from a snowflake schema?JuniorIn which cases would you deliberately denormalize a database schema, and what's the price you pay for it?Mid-levelThe warehouse has a customer dimension, and a customer's city and pricing plan can change. Analysts need revenue reports that take into account which plan the customer was on at the time of purchase. How would you store this dimension?Mid-levelYou're designing a sales data mart for BI. Would you choose a star or a snowflake schema, and how would you decide what one row in the fact table represents?Mid-levelTell me about a time you denormalized a data model for the sake of performance. What price did you have to pay for it?SeniorYou need to keep a history of changes to customer attributes, such as plan, city and segment, in a data warehouse, loading data incrementally once a day. How would you implement a Type 2 SCD, and what pitfalls have you run into?SeniorDesign an analytical data warehouse for a marketplace: orders, products, sellers, buyers, delivery. How would you model the data, and why that way?Senior