I have a question about using Reference. I have several tables that are defined such as below CREATE TABLE iss.accessor ( loaddtlid UUID NOT NULL , seqno SMALLINT NOT NULL , billable VARCHAR(1) DEFAULT 'N' CHECK(billable IN ('N','Y')) NOT NULL , payind VARCHAR(1) DEFAULT 'P' CHECK(payind IN ('P','F')) NOT NULL , code UUID REFERENCE accessorcodes (code) , description CITEXT , ref CITEXT , tractororcarrierflag VARCHAR(1) DEFAULT 'T' CHECK(tractororcarrierflag IN ('T','C')) NOT NULL , tractororcarriernoid UUID , tractorpct DECIMAL(6,4) DEFAULT 0 CHECK(tractorpct BETWEEN 0 AND 1) NOT NULL , charge DECIMAL(7,2) DEFAULT 0 , type VARCHAR(1) DEFAULT 'N' CHECK(type IN ('N','V','D','R','A','S')) NOT NULL , checkdate DATE , checkno CITEXT , processed VARCHAR(1) DEFAULT 'N' CHECK(processed IN ('N','Y')) NOT NULL , itemflag VARCHAR(1) DEFAULT 'N' CHECK(itemflag IN ('N','Y')) NOT NULL , tractorterminalid UUID REFERENCES terminal (terminalid) , cost DECIMAL(7,2) DEFAULT 0 , createdatetime TIMESTAMP , createuser CITEXT , editdatetime TIMESTAMP DEFAULT CURRENT_TIMESTAMP , edituser CITEXT DEFAULT CURRENT_USER ) As you can see there are a few columns which reference back to another table. What I need to know is how does Postgres work with these columns. Can I insert or update a row if those columns are null or are they required to have a non-null value in order for the row to be inserted or saved? Best Regards Michael Gould -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general