We use a table with one column for each attribute of the set. Each row in the
table corresponds to one entity of the entity set. For the entity set
account, see the table of figure 2.14.
We can add, delete and modify rows (to reflect changes in the real world).
A row of a table will consist of an n-tuple where n is the number of
attributes.
Actually, the table contains a subset of the set of all possible rows. We
refer to the set of all possible rows as the cartesian product of the
sets of all attribute values.
We may denote this as
for the account table, where
and
denote the set of all account numbers and all account balances, respectively.
In general, for a table of n columns, we may denote the cartesian product of
by
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