FYI: Avoiding write conflict errors in MS Access clients

This email is semi-off topic; but documents a problem and the server-side 
solution when using MS Access as a client to many (all?) database servers.  I 
decided to post the problem/solution because the MS Access error message is 
very misleading.

For those of you creating applications using PostgreSQL with MS Access 
clients:

PostgreSQL will allow bit fields to hold null values. I consider this to be 
valuable because a null boolean field tells me the information is incomplete 
(a question hasn't been answered, for example); which is, itself, 
information.

MS Access will allow users to insert records into linked tables with null 
values in bit fields.  Unfortunately, when the user tries to update the 
record later, Access will interpret the null value as a data type violation 
and will produce a "Write conflict" error message telling the user that 
someone else has edited the record since the user started editing the record.  
(I was the only user.)  The user can drop the changes or copy them to the 
clipboard; but no changes will be allowed to the data table.

This problem is prevented by using "not null" and assigning default values 
when the table is created in PostgreSQL.  If you are dealing with the problem 
after the fact, use psql to change all of the null values in bit fields to 0 
(or false, for boolean fields).  Then use the "alter table" sql command to 
add default values and the "not null" attribute to the table structure.

Best of luck,

Andrew Gould