You want to write a query that returns the first non-NULL value among col1, col2, and col3, but if all are NULL, it should return 'N/A'. Which SQL expression correctly achieves this?

hard📝 Application Q8 of 15

SQL - CASE Expressions

You want to write a query that returns the first non-NULL value among col1, col2, and col3, but if all are NULL, it should return 'N/A'. Which SQL expression correctly achieves this?

ANULLIF(col1, col2, col3, 'N/A')

BCOALESCE(col1, col2, col3, 'N/A')

CCASE WHEN col1 IS NOT NULL THEN col1 ELSE col2 END

DCOALESCE(NULLIF(col1, col2), col3, 'N/A')

Step-by-Step Solution

Solution:

Step 1: Understand requirement
Return first non-NULL among three columns, else 'N/A'.
Step 2: Match with COALESCE usage
COALESCE returns first non-NULL; adding 'N/A' last covers all NULL case.
Step 3: Evaluate options
COALESCE(col1, col2, col3, 'N/A') matches perfectly; others misuse NULLIF or incomplete CASE.
Final Answer:
COALESCE(col1, col2, col3, 'N/A') -> Option B
Quick Check:
COALESCE with default last handles all NULLs [OK]

Quick Trick: Add default value last in COALESCE to handle all NULLs [OK]

Common Mistakes:

Using NULLIF with more than two arguments
Using incomplete CASE statements
Not providing a default fallback value

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More SQL Quizzes

You want to write a query that returns the first non-NULL value among col1, col2, and col3, but if all are NULL, it should return 'N/A'. Which SQL expression correctly achieves this?

Step 1: Understand requirement

Step 2: Match with COALESCE usage

Step 3: Evaluate options

Final Answer:

Quick Check:

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