First, you'll have to get the ID of the row that contains this window construction.

For this example, assume that the name of the window construction in the IDF is Window Cons A

Note the window construction name must be all uppercase in the query, even if not uppercase in the IDF.

 row_id = "SELECT RowName
              FROM tabulardatawithstrings
              WHERE ReportName='EnvelopeSummary'
              AND ReportForString='Entire Facility'
              AND TableName='Exterior Fenestration'
              AND Value='WINDOW CONS A'"

Next, get the SHGC using the row ID

  shgc = "SELECT Value
              FROM tabulardatawithstrings
              WHERE ReportName='EnvelopeSummary'
              AND ReportForString='Entire Facility'
              AND TableName='Exterior Fenestration'
              AND ColumnName='Glass SHGC'
              AND RowName=row_id"

You can replace Glass SHGC with Glass Visible Transmittance or Glass U-Factor in the second query to get these other properties too.

Here's a query that should prove useful to return a table of characteristics for fenestration:

SELECT DISTINCT t1.Value as Fenestration, t2.Value as SHGC, t3.Value as VT, t4.Value as 'U-Factor'
FROM TabularDataWithStrings t1

LEFT JOIN TabularDataWithStrings t2
              ON t1.RowName = t2.RowName

LEFT JOIN TabularDataWithStrings t3
              ON t1.RowName = t3.RowName

LEFT JOIN TabularDataWithStrings t4
              ON t1.RowName = t4.RowName

WHERE t1.ReportName='EnvelopeSummary'
              AND t1.ReportForString='Entire Facility'
              AND t1.TableName='Exterior Fenestration'
              AND t1.ColumnName='Construction'
              AND t1.Value != ''

              AND t2.ReportName='EnvelopeSummary'
              AND t2.ReportForString='Entire Facility'
              AND t2.TableName='Exterior Fenestration'
              AND t2.ColumnName='Glass SHGC'


              AND t3.ReportName='EnvelopeSummary'
              AND t3.ReportForString='Entire Facility'
              AND t3.TableName='Exterior Fenestration'
              AND t3.ColumnName='Glass Visible Transmittance'


              AND t4.ReportName='EnvelopeSummary'
              AND t4.ReportForString='Entire Facility'
              AND t4.TableName='Exterior Fenestration'
              AND t4.ColumnName='Glass U-Factor'

This returns a table like so:

Fenestration, SHGC, VT, U-Factor
ASHRAE 189.1-2009 EXTWINDOW CLIMATEZONE 4-5, 0.352, 0.442, 2.559