prevent creating join more than once

[mhewedy]

Example input:

{
  "lastName": "ibrahim",
  "department.id": 10,
  "department.name": "hr"
}

Expected SQL:

.....
from employee employee0_ inner join department department1_ on employee0_.department_id=department1_.id 
where employee0_.last_name=? and department1_.id=? and department2_.name=?

Actual SQL:

.......
from employee employee0_ inner join department department1_ on employee0_.department_id=department1_.id 
inner join department department2_ on employee0_.department_id=department2_.id 
where employee0_.last_name=? and department1_.id=? and department2_.name=?

notice the duplicate join on the 2nd line above