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Q: Why are duplicate tuples not allowed in a relation?

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Since relation is a set, and tuples are element of a set, according to set theory, the elements of a set are not ordered.

No Duplicate Tuples - A relation cannot contain two or more tuples which have the same values for all the attributes. i.e., In any relation, every row is unique. • Tuples are unordered - The order of rows in a relation is immaterial. • Attributes are unordered - The order of columns in a relation is immaterial. • Attribute Values are Atomic - Each tuple contains exactly one value for each attribute. It may be noted that many of the properties of relations follow the fact that the body of a relation is a mathematical set.

A relation is defined as a set of tuples. Mathematically, elements of a set have no order among them; hence, tuples in a relation do not have any particular order. In other words, a relation is not sensitive to the ordering of tuples. Tuple ordering is not part of a relation definition because a relation attempts to represent facts at a logical or abstract level. Many logical orders can be specified on a relation but there is no preference for one logical ordering over another.

A relation is defined as a set of tuples. Mathematically, elements of a set have no order among them; hence, tuples in a relation do not have any particular order. In other words, a relation is not sensitive to the ordering of tuples. Tuple ordering is not part of a relation definition because a relation attempts to represent facts at a logical or abstract level. Many logical orders can be specified on a relation but there is no preference for one logical ordering over another.

There are many reasons why SQL allows duplicate tuples (rows):To store non-unique values.To simply remove primary keys, unique indexes, and unique constraints.It allows this if there is no unique constraint.

In a relation we have number of tuple R ={t1,t2,t3.....tn}, nd they follow integrity constraints nd each tuple has a primary key pk.if any of the d two tuple have same attribute. for instance t1=t2 then its pk wud be same too.. but this violates the key constraint.. hence duplicacy not allowed in tuple... enjoy Rijo Rajan

ExtensionThe extension of a given relation is the set of tuples appearing in that relation at any given instance. The extension thus varies with time. It changes as tuples are created, destroyed, and updated.

The entity integrity constraint states that no primary key value can be null. This is because the primary key value is used to identify individual tuples in a relation. Having null value for the primary key implies that we cannot identify some tuples. This also specifies that there may not be any duplicate entries in primary key column key row.

extension in a relation is set of tuples appearing in relation at any given instance . it varies with time .it changes tuple are created ,destroyed and update

In database theory, a relation is defined as a set of tuples that have the same attributes. A tuple is also known as a row or record.

rows are called tuples

The RELATION/table has 9 ATTRIBUTES/columns, and there are 200 TUPLES /rows in the RELATION/table.

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