Question

Is this SQL statement legal?

     SELECT  firstName, lastName
     FROM  Presidents 
     WHERE  (endTerm-beginTerm)>4;

I need to find Presidents which had a term longer than 4 years.
can i use ‘-‘ in this query?
if not, what is the good way?

the data types are endTerm and beginTerm

Answer 1

Add 4 years onto beginTerm, then compare

SELECT  firstName, lastName
     FROM  Presidents 
     WHERE  endTerm > DATE_ADD(beginTerm, INTERVAL 4 YEAR)

This is generally (including using other RDBMS) safer than subtracting or calculating date differences because of how boundaries between periods are handled.