Databases Reference
In-Depth Information
•
*=
: This operator is used to define the corresponding field values based
on the intersection between what the user has selected and the values we
specify. That is, the resulting record set will be the values that "intersect" or
are present in both the user's selection and the values we explicitly define in
our element list.
•
/=
: This one is used to define a symmetric difference (XOR), and the resulting
record set will contain the values that are present in either one set (the user's
selections or the explicitly defined values), but not in both.
Let's walk through some examples to better understand the assignment operators:
•
Sum({$<Year += {2007, 2008}>} Sales)
This expression will return the sales for the years the user has selected and
also for the years 2007 and 2008 whether they are selected or not.
•
Sum({$<Product -= {'Product X'}>} Sales)
This expression will return the sales for the products the user has selected,
but exclude records corresponding to
Product X
.
•
Sum({$<Product *= {'Product X', 'Product Y'}>} Sales)
This expression returns the sales for the current selection, but only for the
intersection of currently selected products, and products
X
and
Y
.
•
Sum({$<ProductNumber *= {"48*"}>} Sales)
This expression returns the sales corresponding to the current selections,
but only for the intersection of the currently selected products and all of the
products whose number begins with
48
.
Set operators
Set modifiers, the part of the set expression that is enclosed in angle brackets, can
also be constructed by combining several different element lists in the field value
definition. Furthermore, the entire set expression can be composed using several
different set modifiers. This is accomplished using set operators.
The different set operators that can be used are:
•
+
: Union
•
-
: Exclusion
•
*
: Intersection
•
/
: Symmetric difference
