Difference between ON and WHERE clauses in SQL table joins

Question

select e.last_name, e.hire_date
from employees e join employees m
on (m.last_name = \'Davies\')
and (e.hire_date > m.hire_date);

select e.last_name, e.hire_date
         


        

Answer 1

The difference lies in when the engine performs the filtering. A "where" represents a filter on the computed product of both tables. The "on" keyword specifies how a join is performed. They are not semantically equivalent even if sometimes they both produce the same outcome.

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