I have an MS Access .mdb which has many tables which have many "Text" fields
defined as "Required = No" and "Allow Zero Length = No".  I have created a
Delphi .exe to allow editing of these tables by using the DbCtrls,
TDatasource, TQuery, and TDatabase.  If a field contains non-blank data, and
I attempt to update it to "empty", upon Posting, I get the error
"Zero-Length not allowed".  I tried trapping the OnChange event to set the
TField of the Dataset to Null by using the TField.Clear method.  I also
tried simply setting TField.AsVariant = Null, with the same results.  If I
change the table definition to "Allow Zero-Length = Yes", everything works
fine ... except I already have an MS Access UI which uses many queries which
use IIF(IsNull(field)).  I would like to avoid having to search through all
the queries looking for these instances and changing them to
IIF(IsNull(field) or field = "").

This seems to me to be a driver issue.  I'm using the Native MSACCESS driver
in Delphi 4 CS.  The fact that I cannot set a field's value to Null seems to
be very inappropriate to me.

I would appreciate any information regarding this situation whether it be "a
new driver is in the works" or "we simply don't support null values for MS
Access".

Thank you.

My Recordset Component has a Feature "Set Empty Strings as NULL Values"
which works around the Problem you have.

see: www.gm-software.de