title: ERROR : single-row subquery returns more than one row
body: <p>I want update department_name to deparment_name and '_1' (example: Administration_1 ) to  list which devide by 2 but here is error,please help to write correctly answer. 
  ERROR : single-row subquery returns more than one row</p>
  
  <pre><code>UPDATE departments
  SET department_name= (SELECT department_name || '_1' from departments)
  WHERE  manager_id=
  (select manager_id from  employees 
  WHERE  MOD( manager_id, 2) != 0);
  </code></pre>