[Solved] Identify the issue in this BEFORE DELETE trigger snippet:IF OLD.user_id IS NULL THEN RAISE EXCEPTION 'User ID missing';END IF; | PostgreSQL

PostgreSQL - Triggers in PostgreSQL

Identify the issue in this BEFORE DELETE trigger snippet:

IF OLD.user_id IS NULL THEN
  RAISE EXCEPTION 'User ID missing';
END IF;

AOLD record is not available in BEFORE DELETE triggers

BTrigger function must return NEW, not OLD

CThe condition should check NEW.user_id instead

DRAISE EXCEPTION cannot be used in triggers

Step-by-Step Solution

Solution:

Step 1: Recall record availability in DELETE triggers
In DELETE triggers, OLD record is available, NEW is not.
Step 2: Check the trigger timing
BEFORE DELETE triggers have access to OLD record, so the condition is valid.
Step 3: Identify the actual problem
Trigger functions must return OLD in DELETE triggers, not NEW.
Final Answer:
Trigger function must return OLD, not NEW -> Option B
Quick Check:
DELETE triggers return OLD to proceed [OK]

Quick Trick: OLD exists in DELETE triggers, NEW does not; return OLD in DELETE triggers [OK]

Common Mistakes:

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Identify the issue in this BEFORE DELETE trigger snippet: