You want to create an UPDATE trigger that fires only when the status column changes. Which condition correctly detects this change?

hard📝 Application Q8 of 15

PostgreSQL - Triggers in PostgreSQL

You want to create an UPDATE trigger that fires only when the status column changes. Which condition correctly detects this change?

AIF NEW.status IS DISTINCT FROM OLD.status THEN

BIF NEW.status = OLD.status THEN

CIF NEW.status IS NULL THEN

DIF OLD.status IS NULL THEN

Step-by-Step Solution

Solution:

Step 1: Understand how to detect column changes
To detect if a column value changed, compare NEW and OLD values.
Step 2: Use IS DISTINCT FROM for NULL-safe comparison
Using IS DISTINCT FROM handles NULL values correctly, unlike simple equality.
Step 3: Analyze options
IF NEW.status IS DISTINCT FROM OLD.status THEN correctly checks if NEW.status differs from OLD.status, including NULL cases.
Final Answer:
IF NEW.status IS DISTINCT FROM OLD.status THEN -> Option A
Quick Check:
Use IS DISTINCT FROM to detect changes safely [OK]

Quick Trick: Use IS DISTINCT FROM to detect changes including NULLs [OK]

Common Mistakes:

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