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Handling Nulls in Dashboard Metrics

EasySQL & Data Manipulation00:00
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Welcome to your interview.

The question is on your right: Handling Nulls in Dashboard Metrics. Take a moment with it first.

Talk your thinking through with me if you like - when you're confident, submit your answer and I'll grade it like a real screen (7/10 or better passes). Discussion and graded submissions share your five interviewer interactions, so spend them well.

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Problem

Explain how you handle NULL values in SQL-backed visualizations without changing the meaning of the data. Focus on when to preserve missing values, when to replace them, and how aggregate functions behave in PostgreSQL.

What This Tests

  • Understanding of NULL semantics
  • Safe use of COALESCE
  • Behavior of COUNT(*), COUNT(column), AVG(), and SUM()
  • Using CASE WHEN to expose missingness in dashboard outputs

Interview Context

In a Synechron visualization workflow, the interviewer is looking for practical SQL judgment: can you make a chart readable without converting missing data into false business signals?