ORA-02270: Error report: no matching unique or primary key for this column list
Foreign keys must reference another table's primary key, or a unique column in the other table (that is, a column with a unique constraint or index of some sort).

teamname is not unique in team, so a foreign key cannot link to it.

you need to either make teamname unique in team, or use a composite foreign key to match `team's composite primary key:

ALTER TABLE entry
    ADD CONSTRAINT entry_team_fk FOREIGN KEY ( teamname, carndate )
        REFERENCES team ( teamname, carndate );


Note: carndate may not be appropriate for this foreign key - just using it as an example. You would know best if there's a date in entry that would match team.carndate.