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A foreign key is a set of attributes in a table that refers to the primary key of another table, linking these two tables. In the context of relational databases, a foreign key is subject to an inclusion dependency constraint that the tuples consisting of the foreign key attributes in one relation, R, must also exist in some other (not necessarily distinct) relation, S; furthermore that those ...
A surrogate key (or synthetic key, pseudokey, entity identifier, factless key, or technical key [citation needed]) in a database is a unique identifier for either an entity in the modeled world or an object in the database. The surrogate key is not derived from application data, unlike a natural (or business) key. [1]
A candidate key, or simply a key, of a relational database is any set of columns that have a unique combination of values in each row, with the additional constraint that removing any column could produce duplicate combinations of values. A candidate key is a minimal superkey, [1] i.e., a superkey that does not contain a smaller one. Therefore ...
Shops and businesses across the U.S. are closed for a day to show support for communities impacted by Trump's immigration policies.
The article talks about the foreign key referencing a Candidate key in the referenced table. I dont think that this is entirely accurate. The foreign key must reference a Superkey, but there is no requirement for that Superkey to also be a Candidate key. Candidate key is a smallest possible superkey, and I'm pretty sure a foreign key can ...
A candidate key (or minimal superkey) is a superkey that can't be reduced to a simpler superkey by removing an attribute. [ 3 ] For example, in an employee schema with attributes employeeID , name , job , and departmentID , if employeeID values are unique then employeeID combined with any or all of the other attributes can uniquely identify ...
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Ulf Michael Widenius (born 3 March 1962), also known as Monty, is a Finnish software programmer. He is the main author of the original version of the open source MySQL database, a founding member of the MySQL AB company, founding member of the MariaDB Foundation and CTO of the MariaDB Company.