>Native RI builder allows to insert NULLs. At least in VFP8 it does. Basically, it gives an error on SEEK command, which is handled in rierror routine and as the end result returns true.

I had tested it only on VFP9 and it doesn't allow to insert NULLs ("trigger failed in child_table"). But I just tested it on VFP8 and there it works fine ! It doesn't have to do with the generated code. Building the RI code in VFP8 and inserting in VFP9 doesn't work either. I didn't try it the other way round as I am not interested in working with VFP8. I suspect that the RI builder wasn't changed between VFP8 and VFP9.
I will try to submit this as a VFP9 bug.

>I'm currently writing my own RI builder where I'll try to avoid things which are not allowed in the Ole Db. Do you have link handy?

http://msdn.microsoft.com/library/default.asp?url=/library/en-us/dv_foxhelp/html/dglrfunsupportedvisualfoxprocommandsfunctions.asp

Thanks a lot for that input !