Zero or many

How to read it

The crow’s foot nearest the entity box sets the maximum at many, and the open circle outside it sets the minimum at zero. In a textbook example, a factory has zero or more employees working at it: a new factory may have none yet.

This is the mark most often paired with One and only one at the other end of a line, for the one-to-many relationship. It differs from One or many only in the circle.

Also searched as: optional many, zero or many symbol.

Look-alikes

The One or many mark has a bar instead of the circle, so at least one record is required. The Zero or one mark has the circle but a single bar instead of the fork.

Differences by notation

In (min, max) notation this is (0,N), and in UML-style multiplicity 0..N, usually written 0..*. In Chen notation as Elmasri and Navathe draw it, an “N” beside the line already means zero, one or many. Barker’s notation, used in Oracle’s CASE tools, draws it as a dashed half-line, “may be”, ending in a crow’s foot, and reads “may be … one or more”.