Interview Q&A / SQL & DBMS
SQL & DBMS interview questions
Joins, keys, normalisation, indexes and transactions for placement and backend interviews.
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- Write a query to calculate a running total of daily sales.
Use SUM(amount) OVER (ORDER BY day) to get a cumulative sum. Add PARTITION BY to restart the total per group, and use ROWS BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW to be explicit.
IntermediateQuick answerCoding1 min read - Write a query to find the highest-paid employee in each department.
Compute MAX(salary) per department in a subquery and join back, or use RANK() OVER (PARTITION BY dept ORDER BY salary DESC) and keep rank 1. Both return all tied employees.
IntermediateQuick answerCoding1 min read