From the help file:
A field cannot always be set to logical and mode. The reason for this is that the and alternative is logically meaningful only if the concerned field is linked to only one other field.
The AND-mode option is only allowed under very strict conditions, imposed by the theory behind the QlikView logic. In order to be used in AND-mode, the following criteria must be fulfilled:
- the field must only exist in one logical table,
- the field must be the second column of no more than two columns, and
- the table must not contain any duplicate records, and
- the table must be loaded using a distinct qualifier. If the table is loaded using a Select statement, you must use a preceding Load distinct *.
Hope it's helpfull,