title: how to calculate the differance between each salary and min salary
body: <p>i'm using sql server 2008 rs1 and I have a problem with a query .
  my table is named : employees 
  table columns are : 
  <code>first name , last name , job title , gender , date of birth and salary</code> . </p>
  
  <p>The required : to display job title, employee name, and the difference between salary of the employee and minimum salary for the job</p>
  
  <p>I try to solve it as this : </p>
  
  <pre><code>SELECT First_Name, Title ,Salary-min(Salary) AS (Differance) FROM Employees;
  </code></pre>
  
  <p>but this cause an error 
  help me please 
  thanks in advance   </p>