I have a calc field:
ExecuteSQL("SELECT \"__uuID\" FROM \"IO\" WHERE \"__uuID\"=?";"";"";Patient::IO_n)
that is 'text' and 'does not store calcs'. In data viewer the calc correctly gets the uuID, but the field remains empty and Data viewer indicates: <index missing>.
A different version of solution using what appeared to be the same fields and calc did work, but I haven't spotted the difference and error in the new version.