Modify logical field

[Alan T]

I want to modify a Yes/No field to NULL, I tried the following:
ALTER TABLE table1 ALTER COLUMN [Resigned] [Logical] NULL

but I got syntax error.

 

[Allen Browne]

YESNO in place of [Logical] (no square brackets) should work, but JET cannot
handle Null in yes/no fields, so the NULL part won't work.

An alternative might be to create an SHORT field, with a validation rule of:
Is Null OR 0 OR -1
so that it behaves like a yes/no but supports Null.

For your reference, here's a list of the field types JET supports:
http://allenbrowne.com/ser-49.html
and some JET DDL examples:
http://allenbrowne.com/func-DDL.html