Rights of All Parties May be Put in Issue

The 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.