 
 CREATE TABLE article (
        filename TEXT PRIMARY KEY,
-       author INTEGER REFERENCES member (member_no) NOT NULL ON UPDATE CASCADE,
+       author INTEGER REFERENCES member (member_no) ON UPDATE CASCADE NOT NULL,
        publish_time TIMESTAMP (0) WITH TIME ZONE NOT NULL,
        update_time TIMESTAMP (0) WITH TIME ZONE NOT NULL,
        section TEXT,

);

CREATE TABLE link_to_review (
       member_no INTEGER REFERENCES member (member_no) NOT NULL ON UPDATE CASCADE,
       link_no INTEGER REFERENCES link (link_no) NOT NULL ON UPDATE CASCADE,
       target_time TIMESTAMP (0) WITH TIME ZONE NOT NULL DEFAULT current_timestamp,
       PRIMARY KEY (member_no, link_no)
);

       link_no SERIAL PRIMARY KEY,
       foreign_phrase TEXT NOT NULL CHECK (length(foreign_phrase) > 0),
       familiar_phrase TEXT NOT NULL CHECK (length(familiar_phrase) > 0),
       foreign_language CHARACTER VARYING (3) REFERENCES language (abbr) ON UPDATE CASCADE NOT NULL,
       familiar_language CHARACTER VARYING (3) REFERENCES language (abbr) ON UPDATE CASCADE NOT NULL,
       link_type TEXT REFERENCES link_type (name) ON UPDATE CASCADE NOT NULL,
       author INTEGER REFERENCES member (member_no) ON UPDATE CASCADE NOT NULL,
       created TIMESTAMP (0) WITH TIME ZONE NOT NULL DEFAULT current_timestamp,
       updated TIMESTAMP (0) WITH TIME ZONE NOT NULL DEFAULT current_timestamp,
       deleted BOOLEAN NOT NULL DEFAULT FALSE
