date difference

[Robert Lee]

Context: I am new to sql and reading 'SQL Queries for Mere Mortals 2nd Edition', chapter 5.

I am using a sample database provided by the textbook. I am having difficulty generating the correct value, number of years a staff has been with a school since a given date.

Q: How many years has each staff been with the school since 2007-10-01? (I am using the standard SQL year format, YYYY-MM-DD.)
Example: There is one staff member who has been with the school since 1982-11-20. So the correct answer to the question for this specific staff member should be roughly 25 years. '2007-10-01' - 1982-11-20 (column Date_Hired)

Process:
Select
cast(cast('2007-10-01' - date_hired as unsigned) / 365 as unsigned ) as Years_with_School
from staff

However, this expression does not provide me with the correct answer. This expression above returned a value of 50539024859423925. I thought I needed to used the keyword integer, but MYSQL does not say is the right syntax. I found out that I had to use the keywords unsigned or signed to convert it to an integer.