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Why duplicate tuples are not allowed in DBMS?
Since relation is a set, and tuples are element of a set, according to set theory, the elements of a set are not ordered.
Characteristics of relations in relational database model?
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.
Why are tuples in a relation not ordered?
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.
Why the tuples in a relation are not ordered?
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.
Duplicate tuples not allowed in a relation?
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
Why does SQL allow duplicate tuples?
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.
What do extension and intentions of relations mean in dbms?
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.
Entity integrity constraint?
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.
What is extension and intension in dbms?
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
What are the relationships that the relational database is named for?
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.
A database user manually notes that The file contains two hundred records each record containing nine fields Use appropriate relational database terminology to translate that statement?
The database contains a table with 200 rows (records) and each row has 9 columns (fields).
What is attributes in database?
A relational database matches data by using common characteristics found within ... do this grouping is called a relational database management system (RDBMS). ...A relation is defined as a set of tuples that have the same attributes. ...
