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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.
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.
What is the sample space of a coin tossed n times?
The sample space consists of 2n ordered n-tuples of the form (X1, X2, ..., Xn) where each Xi = H or T.
What a tuple in a relational model?
A row of a table in relational model is known as tuple - is the easy answer. A tuple is a collection of elements that relate to one another : T = R(e1, e2, ... , en). One can view a collection of similar relations, R, as a table, where the elements of same category are projected underneath one another, and ordered as is suited for the table view. When implementing a relational database, the tuples can be spread all over in a way that suits those that make the storage system, and enables fast retrieval and manipulation of them. So, unless you specify the sorting - "Collating Sequence" of the table, you can expect a new ordering every time you view the table. The elements in the relations are bound together in the same way as rows in a table - but some relations may have more elements - "columns" and really belong to other tables - but is "projected" into the view you see as a table.
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 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.
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 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.
What is tuples in sql?
Tuple is a collection of one or more attributes or rows present in a table.
What is difference between natural join and semi join?
The result of the natural join is the set of all combinations of tuples in R and S that are equal on their common attribute names.The result of the semijoin is only the set of all tuples in R for which there is a tuple in S that is equal on their common attribute names.The point is that natural join is a set of all combinations and semijoin is only the tuples from the first relation not a combination between the two.For example:R1 R2A B B C1 2 2 31 3 3 41 4 5 3R1 (natural join) R2 =A B C1 2 31 3 4whereas R1(semijoin) R2 =A B1 21 3So in a way semijoin selects and returns a table of only the tuples from R1 that have an equal attribute with R2
