Combine node sequences.
The following construct(s) refer to this construct:
An IntersectExceptExpr combines two node sequences by
returning a sequence in document order depending on the operator. Using the
intersect operator all the nodes that occur in both sequences are
returned in document order. Using the except operator all the
nodes that occur in the first operand sequence, but not in the
second.
The following query returns the empty sequence:
<A/> intersect <B/>
The following query returns <A/>:
<A/> except <B/>
