Bug report #9007
MS SQL uniqueidentifier data type is not supported
|Affected QGIS version:||2.0.1||Regression?:||No|
|Operating System:||Easy fix?:||No|
|Pull Request or Patch supplied:||No||Resolution:||duplicate|
|Crashes QGIS or corrupts data:||Yes||Copied to github as #:||17662|
If a MS SQL Spatial layer uses <uniqueidentifier> data type then layer attribute table displays as all nulls and the feature selection selects all features at all time (even if you select a single feature). In my test the <uniqueidentifier> was the PK of the attribute table. Incidentally the this SQL Spatial layer originated from ESRI where the datatype GUID (global id) was use to create it.
I have attached a script to help you recreate this problem. It creates a SQL Spatial table and loads it with some data.