[Solved] Why can NULLIF(expr1, expr2) be considered a shortcut for a specific CASE expression in SQL? — Ans: Because it returns NULL if expr1 equals expr2, else returns expr1, similar to a... | SQL

SQL - CASE Expressions

Why can NULLIF(expr1, expr2) be considered a shortcut for a specific CASE expression in SQL?

ABecause it replaces NULL values with expr2, like a CASE WHEN expr1 IS NULL THEN expr2 ELSE expr1 END

BBecause it always returns the greater of expr1 and expr2, like a CASE statement

CBecause it returns NULL if expr1 equals expr2, else returns expr1, similar to a CASE WHEN expr1 = expr2 THEN NULL ELSE expr1 END

DBecause it counts non-NULL values between expr1 and expr2, like a CASE statement

Step-by-Step Solution

Solution:

Step 1: Understand NULLIF behavior
NULLIF(expr1, expr2) returns NULL if expr1 = expr2; otherwise, it returns expr1.
Step 2: Compare with CASE
This matches the CASE expression:
CASE WHEN expr1 = expr2 THEN NULL ELSE expr1 END
Final Answer:
Because it returns NULL if expr1 equals expr2, else returns expr1, similar to a CASE WHEN expr1 = expr2 THEN NULL ELSE expr1 END -> Option C
Quick Check:
NULLIF(5,5) = NULL equals CASE WHEN 5=5 THEN NULL ELSE 5 END [OK]

Quick Trick: NULLIF mimics CASE for equality check [OK]

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Why can NULLIF(expr1, expr2) be considered a shortcut for a specific CASE expression in SQL?