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Explain Coalesce vs ISNULL. What are the differences in SQL?

SQLeasy0.4 min readPremium

**Architectural Logic**: COALESCE is standard; ISNULL is SQL Server-specific—portability and flexibility differ. **COALESCE**: Standard SQL; returns first non-NULL from list; `COALESCE(a, b, c)`. **ISNULL**: SQL Server; two args only; `ISNULL(a, b)`. **Equivalence**: For two...

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Frequency
Low
Asked at 1 company
Category
487
questions in SQL
Difficulty Split
130E|271M|86H
in this category
Total Bank
1,863
across 7 categories
Asked at these companies
Fractal
Key Concepts Tested
sql

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Expert Answer
83 words

Architectural Logic: COALESCE is standard; ISNULL is SQL Server-specific—portability and flexibility differ. COALESCE: Standard SQL; returns first non-NULL from list; COALESCE(a, b, c). ISNULL: SQL Server; two args only; ISNULL(a, b). Equivalence: For two args, same result. Differences: COALESCE portable; handles multiple fallbacks. ISNULL: type of first arg; COALESCE can change type. Example: COALESCE(phone, email, 'N/A') vs ISNULL(phone, 'N/A'). Best Practice: COALESCE for portability and chains; ISNULL when SQL Server and two args suffice. Edge Case: Type handling differs (e.g., VARCHAR vs INT).

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