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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 is tuples in sql?
Tuple is a collection of one or more attributes or rows present in a table.
Which construct in SQL is used to test whether a subquery has any tuples in its result?
Exists
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.
How do you calculate the range in maths?
You calculate the range by subtracting the first and last number in the sequence
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.
Why selection query is first done than projection query?
Selection has more power to reduce size (Number of rows) while projection can not reduce number of tuples
What angle add up to 150?
How about 1 and 149. There are an infinite number of pairs, an infinite number of triplets, an infinite number of quadruplets, ... an infinite number of n-tuples. And n, itself, can be infinitely large.
Tuple in dbms?
rows are called tuples
What is a full outer join sql?
Join is used to combine related tuples from two relations . Full outer join cover all possible combinations of common tuples.
Why do duplicate tuples not allowed in a reaction?
Duplicate tuples are not allowed in a reaction because each reactant and product must be listed only once to accurately represent the stoichiometry of the reaction. Including duplicate tuples would result in an incorrect representation of the reactants and products involved, leading to inaccuracies in the reaction equation.
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.
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.
What provides the ability to query information from the database and to insert tuples into delete tuples from and modify tuples in the database?
SQL (Structured Query Language) provides the ability to query, insert, delete, and modify data in a database. It is a standard language used for managing and manipulating relational databases. By using SQL commands, users can interact with the database to retrieve, add, change, or remove data as needed.
What is spurious tuples?
A spurious tuple is a record in database that get created when two tables are joined badly. Spurious tuples are created when two tables are joined on attributes that are neither primary keys nor foreign keys. Hopes this will help you .
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.
