Option 2 says the Identification vaiable can represent a single variable or a collection -- It is corerct right, since we can use it like WHERE m.title='some title' and WHERE d.movies IS EMPTY.
An identification variable designates an instance of an entity bean abstract schema type or an element of a collection of entity bean abstract schema types instances.
An identification variable thus always designates a reference to a single value. It is declared in one of two ways; as a range variable or a collection member identification variable:
1. A range variable is declared using the abstract schema name of an entity bean 2. A collection member identification variable is declared using a collection-valued path expression.
For Example:
In the FROM clause declaration IN(o.lineItems) l, the identification variable l evaluates to any LineItem value directly reachable from Order.
The cmr-field lineItems is a collection of instances of the abstract schema type LineItem and the identification variable l refers to an element of this collection. The type of l is the abstract schema type of LineItem.
Hope this clarifies it.
Post by:autobot
We're all out of roofs. But we still have tiny ads:
a bit of art, as a gift, that will fit in a stocking