The following attributes cannot be NULL. All other attributes can be NULL $...$ but remember that

attributes in Primary Keys also cannot be NULL, even though you don't specify NOT NULL for them.

$$ In Persons: personName

$$ In Theaters: theaterName

$$ In Theaters: theaterFeePerDay

Also, the following must be unique for the specified table. That is$,$ there cannot be identical rows in that

table that have exactly the same $($non$-$NULL$)$ values for all of those attributes $($composite unique

constraint$).$