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SQLtest.online
Task 8:
You notice that the row count in a fact table suddenly dropped by 30% after a deployment. What checks would you run first, and how would you determine whether the issue came from extraction, transformation, joins, filtering logic, or the final load step?

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Who is a Data Engineer?

A Data Engineer designs and maintains systems that collect, transform, and deliver data for analytics and business decisions.

What does a Data Engineer do?

  • Builds reliable ETL/ELT pipelines from multiple data sources.
  • Prepares clean and structured datasets for analysts and data scientists.
  • Designs data warehouse schemas (fact and dimension tables).
  • Monitors data quality, freshness, and pipeline failures.
  • Optimizes query performance and data processing costs.

What should a Data Engineer know?

  • Strong SQL: joins, aggregations, window functions, and query tuning.
  • Data modeling: normalization, denormalization, star and snowflake schemas.
  • Pipeline orchestration and scheduling principles.
  • Batch and streaming concepts, incremental loading, and idempotency.
  • Cloud storage, data warehouses, and observability basics.

This page helps you practice interview-style Data Engineering questions on SQLTest.online.

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SQL in 10 Minutes a Day by Ben Forta
SQL in 10 Minutes a Day by Ben Forta
Whether you're an application developer, database administrator, web application designer, mobile app developer, or Microsoft Office users, a good working knowledge of SQL is an important part of interacting with databases. And Sams Teach Yourself SQL in 10 Minutes offers the straightforward, practical answers you need to help you do your job.