There is nothing to update in first table Emp_id what links both tables. So if you trying to get salary of an employee you either have already person's ID or you will find out through matching of employee name and department against Emp table. Once you get that ID then you can query salary table for that person salary
There is nothing to reflect in first table. In reality you do want to only update salary in salary table. If you start adding new salaries with same employee ID how do will you find what is that person actual salary from numerous records you will have?
Hello dharam if u know the concept of Primary and Foriegn key than it wil be very easy for u to maintain the things as you cant add any salary for an id that does not exist in parent table so rather than putting an trigger on it, it would be better if you use this concept.