PostgreSQL - Triggers in PostgreSQL
Why is it important that a PostgreSQL trigger function for data validation returns NEW when used in a BEFORE INSERT or UPDATE trigger?
Why is it important that a PostgreSQL trigger function for data validation returns NEW when used in a BEFORE INSERT or UPDATE trigger?
hard📝 Conceptual Q10 of 15
Step-by-Step Solution
Solution:
Step 1: Understand trigger return values
In BEFORE triggers, returning NEW saves the row with possible changes.Step 2: Effect of returning NULL
Returning NULL cancels the insert or update operation.Final Answer:
Returning NEW allows the modified row to be saved; returning NULL cancels the operation -> Option AQuick Check:
Return NEW to save row, NULL to cancel [OK]
Quick Trick: Return NEW to save changes, NULL to cancel insert/update [OK]
Common Mistakes:
- Thinking returning NULL saves row
- Confusing OLD with NEW
- Assuming recursive trigger calls
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