e rights of the several parties, plaintiff as well as defendant, may be put in issue, tried, and determined in such action; and when a sale of the premises is necessary, the title must be ascertained by proof to the satisfaction of the court before the sale can be ordered; except that where there are several unknown persons having an interest in the property, their rights may be considered together in the action, and not as between themselves.

SOURCE: CCP § 759.