ll = .t. llNull = null =messagebox(ll and llNUll) =messagebox(ll or llNUll) =messagebox(not llNull) ll = .f. =messagebox(ll and llNUll) =messagebox(ll or llNUll) =messagebox(not llNull)However, try with char fields.
>Null values persist through logical expressions in most cases. The following table describes the behavior of null values in logical expressions. > >Logical expression Result if x=TRUE Result if x=FALSE Result if x=.NULL. >x AND .NULL. .NULL. FALSE .NULL. >x OR .NULL. TRUE .NULL. .NULL. >NOT x FALSE TRUE .NULL. > >