Coverfox Senior Manager Interview Questions and Answers

The output of 4 joins is a result set that combines data from multiple tables based on specified conditions.

• Joins are used to combine rows from two or more tables based on a related column between them.

• Types of joins include INNER JOIN, LEFT JOIN, RIGHT JOIN, and FULL JOIN.

• Processing of joins involves matching rows from the tables based on the specified join condition.

• The output of 4 joins would involve combining data ...read more

Self joins between tables with CTE are used to join a table to itself using Common Table Expressions.

• Self joins are used when you need to compare rows within the same table.

• CTE is used to create a temporary result set that can be referenced multiple times in a query.

• Example: SELECT e1.employee_id, e2.manager_id FROM employees e1 JOIN employees e2 ON e1.manager_id = e2.employee_id

Optimizations in Spark involve tuning configurations, partitioning data, using efficient transformations, and caching intermediate results.

• Tune configurations for memory and parallelism

• Partition data to distribute workload evenly

• Use efficient transformations like map, filter, and reduce

• Cache intermediate results to avoid recomputation