You want to ensure that a user's email is unique and not empty using a trigger. Which approach correctly combines data validation and uniqueness check in PostgreSQL?

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PostgreSQL - Triggers in PostgreSQL

ACreate a BEFORE INSERT OR UPDATE trigger that raises exception if NEW.email is empty or exists in the table

BUse a UNIQUE constraint on email column only, no trigger needed

CCreate an AFTER INSERT trigger that deletes duplicates after insertion

DUse a trigger that sets empty emails to a default value

Step-by-Step Solution

Solution:

Step 1: Understand validation needs
Email must be non-empty and unique before saving data.
Step 2: Choose trigger timing and logic
BEFORE INSERT OR UPDATE trigger can check NEW.email and query table for duplicates, raising exception if invalid.
Final Answer:
Create a BEFORE INSERT OR UPDATE trigger that raises exception if NEW.email is empty or exists in the table -> Option A
Quick Check:
Validate and check uniqueness before insert/update [OK]

Quick Trick: Use BEFORE trigger to check and stop invalid data [OK]

Common Mistakes:

Relying only on UNIQUE constraint without empty check
Using AFTER trigger to fix duplicates (too late)
Setting default instead of raising error

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You want to ensure that a user's email is unique and not empty using a trigger. Which approach correctly combines data validation and uniqueness check in PostgreSQL?

Step 1: Understand validation needs

Step 2: Choose trigger timing and logic

Final Answer:

Quick Check:

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