Gain WGS84 decimal to locate some cities in Google Map.
I don't know how to convert the value of the RT90 coordinate system into WGS84 in SQL Server.
This page may be of assistance:
in postgis you can use this sql query for RT90(SRID=3021) to WGS84(SRID=4326) :
beside this you can check out this REST-service which converts coordinates between RT90 (Rikets Triangelnät or Swedish Grid) and WGS84 decimal.
and the last thing is that i want to say, you can use SQL Server Spatial Tools for querying spatial queries...
i hope it helps you....