title: Group By with Multiple Unique Constraints Condition
body: <p>I need to fetch data from below mentioned table Sizes where data will be unique by Code,ArtId and Size OR unique By Code,ArtId and SizeIndex (i.e There are two unique constraints).How I can get unique records in single select statement using group by . </p>
  
  <pre><code>ArtId | SizeIndex       | Size           | Description          |   Code
  001   | 000000000001111 | X              | TEST                 |   01
  002   | 000000000001111 | XL             | NULL                 |   02
  003   | 000000000001111 | L              | NULL                 |   03
  004   | 000000000009999 | SL             | TEST2                |   04
  005   | 000000000009999 | ML             | LIGHT                |   05
  006   | 000000000009999 | M              | Filter element,Air   |   06
  </code></pre>
  
  <p>Your help will be highly appreciated </p>