Tuple is a collection of one or more attributes or rows present in a table.
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.
Exists
select
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.
QBE is an advantage over SQL as it is a visual technique allowing non-experts to do searches, as it is simple to understand.
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.
Exists
Join is used to combine related tuples from two relations . Full outer join cover all possible combinations of common tuples.
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.
DML is a subset of SQL (Structured Query Language) that is used to insert, delete and revise records (or 'tuples') in a relational database. The precise definition of DML varies considerably with the database system with which it is associated.
DML is a subset of SQL (Structured Query Language) that is used to insert, delete and revise records (or 'tuples') in a relational database. The precise definition of DML varies considerably with the database system with which it is associated.
Since relation is a set, and tuples are element of a set, according to set theory, the elements of a set are not ordered.
rows are called tuples
One can find an SQL formatter from: SQL Format, Free Formatter, Poor SQL, T-SQL Tidy, Stack Overflow, SQL Inform, Apex SQL, SQL Parser, Red Gate software, to name a few.
T-SQL is Microsoft's version of the generic SQL langauge to be used with, for example, Microsoft SQL Server.
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.
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.