What does the following window function return for the third row? LAG(salary, 2, 0) OVER (ORDER BY hire_date)

Question

SQL Fundamentals — Hard

What does the following window function return for the third row? LAG(salary, 2, 0) OVER (ORDER BY hire_date)

Accepted Answer

The LAG function with a second argument of 2 looks back 2 rows from the current row. In this case, it returns the salary of the first row (2 rows before the third row), ignoring the default value of 0.