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Primary key. In the relational model of databases, a primary key is a specific choice of a minimal set of attributes ( columns) that uniquely specify a tuple ( row) in a relation ( table ). [a] [1] Informally, a primary key is "which attributes identify a record," and in simple cases constitute a single attribute: a unique ID.
Surrogate key. 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.
Unique identifier. A unique identifier ( UID) is an identifier that is guaranteed to be unique among all identifiers used for those objects and for a specific purpose. [1] The concept was formalized early in the development of computer science and information systems. In general, it was associated with an atomic data type .
Natural key. A natural key (also known as business key [1] or domain key [2]) is a type of unique key in a database formed of attributes that exist and are used in the external world outside the database (i.e. in the business domain or domain of discourse ). [3] In the relational model of data, a natural key is a superkey and is therefore a ...
In a relational database, a weak entity is an entity that cannot be uniquely identified by its attributes alone; therefore, it must use a foreign key in conjunction with its attributes to create a primary key. The foreign key is typically a primary key of an entity it is related to. The foreign key is an attribute of the identifying (or owner ...
Composite key. In database design, a composite key is a candidate key that consists of two or more attributes, [1] [2] [3] (table columns) that together uniquely identify an entity occurrence (table row). A compound key is a composite key for which each attribute that makes up the key is a foreign key in its own right. [citation needed]
Serge Massar was born in Zambia in 1970. [2] He obtained a degree in physics, then a PhD from the Université libre de Bruxelles (ULB) in 1991 and 1995, respectively. [2] He completed his post-doctoral research at Tel Aviv University from 1995 to 1997, and subsequently at Utrecht University from 1997 to 1998. [2] [3]
In biology, an identification key, taxonomic key, or biological key is a printed or computer-aided device that aids the identification of biological entities, such as plants, animals, fossils, microorganisms, and pollen grains. Identification keys are also used in many other scientific and technical fields to identify various kinds of entities ...