Introduction
Syntax of PL/pgSQL
Function parameters
Instruction
Brilliant! Now, let's complete the last recap exercise.
Exercise
Create a scalar function with a signature of get_employees_salary(emp_id integer) that returns the salary value corresponding to a given employee ID.
The function should return the related salary value (of NUMERIC type) from the salary table for a given emp_id.
If the given emp_id doesn't exist in the person or salary table, we should raise an exception in the following format:
'Employee with ID XXX doesn't exist!'
