In Oracle, a NOT NULL constraint on a table column of VARCHAR in essence says: "You need to put at least 1 character for a value". There is no such thing as a zero-length string in Oracle, it's either NULL or it has some characters.
To make Postgres perform an equivalent column edit, I am considering defining table columns like ... mycol VARCHAR(20) NOT NULL CHECK (mycol !='')
Is there any drawback to this? Is there a better way to do it? Any thoughts? how about ....
mycol VARCHAR(20) NOT NULL CHECK (length(mycol) > 0)
or even
mycol VARCHAR(20) CHECK (length(mycol) > 0)
That seems like the best choice. Equality checks should be faster than length detection.