An entity set that does not possess sufficient attributes to form a
primary key is called a weak entity set. One that does have a primary
key is called a strong entity set.
For example,
The entity set transaction has attributes transaction-number, date and amount.
Different transactions on different accounts could share the same number.
These are not sufficient to form a primary key (uniquely identify a transaction).
For example,
The entity set transaction has attributes transaction-number, date and amount.
Different transactions on different accounts could share the same number.
These are not sufficient to form a primary key (uniquely identify a transaction).
