Real questions from top companies in SQL · medium
Write a query to remove duplicate records from a table while retaining the earliest entry.
Write a query to retain only the latest record and delete others in case of duplicates.
Write a query to select the latest record based on a time_of_insertion column.
Write a self join query to get the manager's name for each employee.
Write an SQL query to find the top 3 performing products in each category
Write code to find the third-highest salary in a dataset using Pandas.
Write optimized SQL queries involving window functions, CTEs, and joins.
Write queries combining Joins and Group By operations.
Your Kafka consumer shows significant lag during peak hours. What strategies would you employ to reduce lag and ensure timely data processing?
map() vs mapPartitions(): Highlight the difference between map (row-level transformation) and mapPartitions (partition-level transformation).
repartition() vs coalesce(): Explain when to use repartition() (increases partitions) vs coalesce() (reduces partitions).
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