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Before we talk about the relational model in more detail, let us first define some very basic terms used in this model.
Tuple
Every row in a table shows a record and is called a tuple. A table containing 'n' attributes in a record is called n-tuple.
Attribute
The name of every column in a table is used to interpret its meaning and is known as an attribute. Every table is called a relation.
For instance, Figure shows a relation PERSON. The columns NAME, PERSON_ID, AGE and ADDRESS are the attributes of PERSON and every row in the table represents a separate tuple (record).
Relation Name: PERSON
PERSON_ID
NAME
AGE
ADDRESS
TELEPHONE
1
Sanjay Prasad
35
b-4,Modi Nagar
011-25347527
2
Sharad Gupta
30
Pocket 2, Mayur Vihar.
023-12245678
3
Vibhu Datt
36
c-2, New Delhi
033-1601138
Figure: An extended PERSON relation
Inconsistent Analysis : The problem as given with transactions T1 and T2 where two transactions interleave to make incorrect result during an analysis by Audit is the instance of s
Synonyms It allows short names or alternative names for objects. Example : CREATE SYNONYM D30 FOR EMPD30; Now if we give command:
What is multiple relationship ?
In case of entity integrity, the primary key may be declared? In a case of entity integrity primary key may be not Null.
Explain degree of relation? Degree of a Relation - The degree or arity of a relation is the number of attributes n of its relation schema.
What are partial, alternate,, artificial, compound and natural key? Partial Key: It is a set of attributes that can uniquely recognize weak entities and that are related to s
What is inheritance? Define it in detail? Inheritance Inheritance can be at the levels of types, or at the level of tables we first consider inheritance of types, then i
Mention the various user privileges All privileges directly granted to the user or role. All privileges granted to roles that have been granted to the user or role.
Determine the Disadvantages of file based systems Some of the disadvantages of file based systems are like this: Data redundancy and inconsistency: the dissimilar applic
Can a domain, assigned to a data element be changed? Yes. We can do so by just overwriting the entry in the field domain.
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