| jimmy |
Posted: Mar 18, 2007 05:49:15 AM |
Total Post: 9
Joined: Feb, 2007
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| plz tell me the diff between tuple and attribute and also about composite key and super key |
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 deal |
| Posted: Mar 18, 2007 10:43:50 AM |  |
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Total Post: 21
Joined: Nov, 2006
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Attributes are represented as columns in a table and
each attribute in a relation is unique and contains some value.
The no, of attributes in a relation is called degree of relation
Tuple is a row in a table.The number of tuples in a relation
is called cardinality of relation.
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| deal |
| Posted: Mar 18, 2007 10:48:59 AM | |
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Total Post: 21
Joined: Nov, 2006
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As far as I know a
composite key is a primary key that consists of more than
one column whereas as super key can consist of
a single or more than one column which idetifies a row uniquely.
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| Rush |
| Posted: Mar 19, 2007 12:16:44 AM | |
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Total Post: 127
Joined: Jan, 2007
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hi,
composit key may or may not uniquly identify an entity.but super key alwase.
that's why primary key is also called minimum superkey.
from
Rupesh
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