OR Searches, AND Searches, and Hierarchy Lookup Fields 

Searching within a multi-valued hierarchy lookup search tab has special behavior and special meaning, especially as it relates to AND searches.

With an OR search, when you select a parent node in the hierarchy, the search results of each child are ORed together. MDM illustrates this by automatically selecting all of its children as if each of the children were individually selected, as shown in the figure below.

If you then unselect one of the children (using Ctrl + Click to unselect the node), the other children remain selected and are ORed together, but MDM automatically unselects the parent, as shown in the following figure.

A taxonomy lookup search tab only permits single selection. Automatic selection/unselection of parents/children applies only for hierarchy lookup search tabs that permit multiple selection.

With an AND search, when you select a parent node in the hierarchy, the search results of each child are ORed together, to be ANDed together with other search selections. Because multiple selections are ANDed together, MDM does not automatically select all of its children.

In fact, when you select any node in the hierarchy, MDM automatically unselects all of its ancestors and all of its descendents.

The search logic and selection/unselection behavior for OR and AND searches in a hierarchy lookup search tab is summarized in the following table.

Search	Description
OR	·        Selecting an internal node causes all of its descendants to be selected and their results ORed together, to be ORed with other selections. ·        Selecting an internal node is the same as selecting each descendent separately, which can be used as a shortcut to select all but a few children, by first selecting the parent and then unselecting some children. ·        Unselecting any node causes all of its ancestors to be unselected as well. (If the parent node were to remain selected, it should produce the same results as if all of its descendants were selected, but one of the descendents was just unselected.)
AND	·        Selecting an internal node causes the results of all of its descendants to be ORed together as a single selection, to be ANDed with other selections. ·        Selecting an internal node is different than selecting each descendant separately, which ANDs the results of all selected descendants. ·        Selecting any node causes all of its ancestors and descendants to be unselected. (Because multiple selections are ANDed together, if an ancestor and descendant were to both remain selected, it would be the same as just having the descendant selected, so it would be confusing to leave them both selected.) ·        Unselecting a node just unselects that node.