I loaded spatial data in ms sqlserver. Most data are in WGS 84 coordinates, but some are in Pulkovo 42. WGS 84 objects are visible well in QGIS. I checked it in 2.4 and 2.16 versions. But Pulkovo 42 features are invisible. It depends only on value of [geometry_columns].[srid] field. When I change value from 4284 to 4326, features became visible. Records in [spatial_ref_sys] don't affect the result.