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Compare Join Types in Reporting

EasySQL & Data Manipulation00:00
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Your question is Compare Join Types in Reporting. Take a moment with it on the right.

Talk me through your thinking if you like. When you're confident, submit your answer and I'll grade it like a real screen (7/10 or better passes).

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Problem

Context

Join type selection directly affects which rows appear in a result set, which is critical when building reports in PostgreSQL or Infosys data platforms. A wrong join can silently exclude records or introduce unexpected NULL values.

Question

You are asked to explain the difference between INNER JOIN, LEFT JOIN, and RIGHT JOIN. Describe which rows each join returns, how unmatched rows are handled, and how the result changes when one table has records with no match in the other table.

Use a simple reporting example such as employees and departments, or customers and orders, to illustrate your explanation. You should also clarify whether LEFT JOIN and RIGHT JOIN are fundamentally different or just mirror images of each other.

Scope Guidance

The interviewer expects a clear conceptual explanation, not a complex query. Focus on row inclusion logic, NULL behavior, and when you would choose each join type in practice.