[Solved] Consider this trigger function:CREATE FUNCTION check_salary() RETURNS trigger AS $ BEGIN IF NEW.... $ LANGUAGE plpgsql;What will happen if you update a row setting salary = 0? | PostgreSQL

PostgreSQL - Triggers in PostgreSQL

Consider this trigger function:

CREATE FUNCTION check_salary() RETURNS trigger AS $$ BEGIN IF NEW.salary <= 0 THEN RAISE EXCEPTION 'Salary must be positive'; END IF; RETURN NEW; END; $$ LANGUAGE plpgsql;

What will happen if you update a row setting salary = 0?

AThe update succeeds and salary is set to 0

BThe update fails with an error

CThe salary is set to 1 automatically

DThe trigger does not run on updates

Step-by-Step Solution

Solution:

Step 1: Understand the trigger condition
The trigger raises an exception if salary is less than or equal to zero.
Step 2: Apply to salary = 0 update
Since 0 <= 0, the exception triggers and update fails.
Final Answer:
The update fails with an error -> Option B
Quick Check:
Trigger blocks invalid salary update [OK]

Quick Trick: Triggers can block invalid updates by raising exceptions [OK]

Common Mistakes:

Assuming update succeeds
Thinking trigger only runs on insert
Believing salary auto-corrects

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Consider this trigger function:

Step 1: Understand the trigger condition

Step 2: Apply to salary = 0 update

Final Answer:

Quick Check:

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