Some context would help but some (possibly relevant) possibilities:
1: If you have relation with 5 attributes you can generate tuples with all 5
attributes OR you can generate tuples with a subset of those attributes.
Seems obvious but often these kinds of definitions are.
2: When looking a
On 02/15/11 2:01 PM, Alpha Beta wrote:
Hi,
while reading about databases, I didn't understand what can be subset
of attributes, see the following :
Let Ri (Xi) be a relation sheme, where Xi is a set of attributes. and
if t is a tuple for Ri (Xi) and Y is a subset of Xi, then t[Y] denote
th
