Having mentioned possible collisions between the outer and the inner legs of a join, it should also be mentioned that a similar problem could occur between the function and the INSERT operation.

As such, the NLJOIN does not act as a classical join with two input legs, but facilitates access to the XML data for the XSCAN operator.

Join operators such as HASH, MERGE SCAN and (in some situations) NESTED LOOP can also benefit from asynchrony by simultaneously executing the inner and outer legs of the join operator.