Full Outer Join — Solution & ExplanationProblems / Full Outer Join / EditorialApproach

FULL OUTER JOIN budget and actuals on both department and quarter. This preserves rows from both sides.

COALESCE department and quarter from both tables for the output columns (since either side might be NULL).

COALESCE the amounts with 0 to handle NULLs, then compute the difference.

Key InsightFULL OUTER JOIN is the most inclusive join type. It's essential for reconciliation tasks where you need to see all data from both sources, including items that exist in only one. HR has budget rows but no actuals in Q1/Q2; R&D has actuals but no budget.Hints

FULL OUTER JOIN keeps all rows from both sides, filling NULLs where there's no match.

Use COALESCE on both department and quarter for the output since either side could be NULL.

The R&D department only exists in actuals, and HR only in budget for this dataset.

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