Add expansion of field variables in SQL queries.
Add expansion of field variables in SQL queries.

googledatalab/datalab,craigcitro/datalab,parthea/datalab,googledatalab/datalab,craigcitro/datalab,yebrahim/datalab,googledatalab/datalab,parthea/datalab,parthea/datalab,yebrahim/datalab,yebrahim/datalab,craigcitro/datalab,googledatalab/datalab,googledatalab/datalab,parthea/datalab,googledatalab/datalab,craigcitro/datalab,parthea/datalab,yebrahim/datalab,yebrahim/datalab,craigcitro/datalab,parthea/datalab