I am trying to create tables for two objects, "Document" and "Document Review". A Document Review can have many Documents in it.
I am thinking of creating a table T_Doc_Rev with DOC_REV_ID as primary key. This is used as a foreign key in T_Doc table; however, the foreign DOC_REV_ID in T_Doc table is nullable because a document may not have an existing document review at one time.
My question is, is it ok for the DOC_REV_ID foreign key to be nullable in T_Doc table? I am asking this because I heard it is a bad practice to have a nullable foreign key.