Database tables within the WebSphere Commerce database schema are organized into functional groups, called data models. The referential integrity relationship between database tables is illustrated using the following symbols:
A
rounded, dotted rectangle represents a weak dependent entity. Instances of
a weak dependent entity cannot be uniquely identified without determining
its relationship to other entities. The primary key to an instance of a
weak dependent entity consists entirely of foreign keys.
A
rounded, solid rectangle represents a strong dependent entity. Instances
of a strong dependent entity cannot be uniquely identified without
determining its relationship to other entities. The primary key to an
instance of a strong dependent entity contains foreign keys, but does not
consist entirely of foreign keys.
A
rectangle represents an independent entity. Instances of an independent
entity can be uniquely identified without determining its relationship to
other entities. The primary key to an instance of an independent entity
does not contain any foreign keys.
A solid relationship line represents an
identifying relationship. An identifying relationship occurs when
instances of the child entity are identified through association with a
parent entity. The primary key attributes of the parent entity become
primary key attributes of the child.
A dotted relationship line with a solid
relationship symbol represents a mandatory non-identifying relationship. A
mandatory non-identifying relationship occurs when key attributes from the
parent entity must become non-key attributes of the child entity. That is,
the inherited non-key attributes of the child entity in this relationship
cannot be NULL.
A dotted
relationship line with a solid and open relationship symbol represents an
optional non-identifying relationship. An optional non-identifying
relationship occurs when foreign keys from the parent entity can become
non-key attributes of the child entity. That is, the inherited non-key
attributes of the child entity in this relationship can be NULL.
A relationship line that links back to the
original table indicates a recursive relationship. Recursive relationships
must be optional non-identifying relationships.