QWS will allow SharePoint designers to define a primary key field and foreign key field in the lists. You can also replicate some fields from the parent list in the child lists so that those fields are available to be displayed and searched.
The List Form can auto-fill the foreign key field and any of the replicated fields so that the user does not have to enter the data manually. This ensures that all these fields will be populated properly and consistently.
Provides the capability to lookup multiple fields from multiple lists in any site or site collection (as long as the sites are still in one configuration database). The ability to Auto-Fill a field based on value of a field that belongs to a parent field. The parent field can be a lookup field or a cross-site lookup field. This feature ensures data consistency and correctness when the value from the parent field is replicated in the target field.
The List Form can create or update items on other lists when an item is saved in one list.
Any webparts in the QWS that enable you to delete a record can check for the other lists for any child records. If there are one or more child records, the delete operation will result in an error.