title: Find missing numbers in a column
body: <p>I have this column in T-SQL:</p>
  
  <pre><code> 1
   2
   3
   7
   10
  </code></pre>
  
  <p>have SQl a function for detect the missing numbers in the sequence 4,5,6 and 8,9 
    I have try 
              something like 
              if ( a-b >1 )  then we have a missing number  </p>
  
  <p>with coalesce but i dont understand .
  Thanks by any orientation</p>