title: order by in string_agg does not seems to work
body: <p>I have a table #tmp like this:</p>
  
  <pre><code>recid       DefaultDimension    DefaultDimensionName    line_no
  5637423499  Default             Employee                7
  5637423499  1001                Product                 8
  5637423499  100                 Region                  2
  5637423499  1                   Routing                 17
  5637423499  115                 Section                 5
  5637423499  999                 Unit                    6
  5637423499  1510                Branch                  3
  5637423499  A                   CabinClass              14
  5637423499  0B                  Carrier_Property        9
  5637423499  103                 Channel                 16
  5637423499  104                 Department              4
  5637423499  113                 Division_CustomerType   1
  </code></pre>
  
  <p>I want to concat DefaultDimension and DefaultDimensionName columns based on ascending order of line_no</p>
  
  <p>Here is the query I wrote but I'm not getting it in order:</p>
  
  <pre><code>select recid, 
  STRING_AGG(DefaultDimension, '-')  WITHIN GROUP (ORDER BY line_no ASC) DefaultDimension,
  STRING_AGG(DefaultDimensionName, '-') WITHIN GROUP (ORDER BY line_no ASC) DefaultDimensionName 
  from #tmp
  group by recid
  </code></pre>
  
  <p>Result:</p>
  
  <pre><code>recid       DefaultDimension                                    DefaultDimensionName
  5637423499  113-A-103-1-100-1510-104-115-999-Default-1001-0B    Division_CustomerType-CabinClass-Channel-Routing-Region-Branch-Department-Section-Unit-Employee-Product-Carrier_Property
  </code></pre>
  
  <p>As you can see CabinClass should come at 3rd last position but it's coming at 2nd position.</p>