You want to create a trigger that logs changes to a salary column only when the salary is updated to a higher value. Which trigger condition and record access correctly implements this in PostgreSQL?
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PostgreSQL - Triggers in PostgreSQL
You want to create a trigger that logs changes to a salary column only when the salary is updated to a higher value. Which trigger condition and record access correctly implements this in PostgreSQL?
AIF OLD.salary > NEW.salary THEN INSERT INTO log_table VALUES (OLD.id, OLD.salary); END IF;
BIF NEW.salary < OLD.salary THEN INSERT INTO log_table VALUES (NEW.id, NEW.salary); END IF;
CIF NEW.salary = OLD.salary THEN INSERT INTO log_table VALUES (NEW.id, NEW.salary); END IF;
DIF NEW.salary > OLD.salary THEN INSERT INTO log_table VALUES (NEW.id, NEW.salary); END IF;
Step-by-Step Solution
Solution:
Step 1: Understand the condition for logging
The trigger should log only when the new salary is greater than the old salary, so the condition is NEW.salary > OLD.salary.
Step 2: Use correct record variables for UPDATE
The new salary and id come from NEW because the row is updated with new values.
Final Answer:
IF NEW.salary > OLD.salary THEN INSERT INTO log_table VALUES (NEW.id, NEW.salary); END IF; -> Option D
Quick Check:
Log when NEW > OLD salary = B [OK]
Quick Trick:Compare NEW and OLD to detect increases, then log NEW data [OK]
Common Mistakes:
Reversing NEW and OLD in condition
Logging when salary decreases
Using equality instead of greater than
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