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At the most basic definition, "a key is a unique identifier", [1] so unique key is a pleonasm. Keys that are within their originating entity are unique within that entity. Keys that migrate to another entity may or may not be unique, depending on the design and how they are used in the other table.
Some databases provide UUID/GUID as a possible data type for surrogate keys (e.g. PostgreSQL UUID [3] or SQL Server UNIQUEIDENTIFIER [4]). Having the key independent of all other columns insulates the database relationships from changes in data values or database design [5] (making the database more agile) and guarantees uniqueness.
In the relational model of databases, a primary key is a designated attribute that can reliably identify and distinguish between each individual record in a table.The database creator can choose an existing unique attribute or combination of attributes from the table (a natural key) to act as its primary key, or create a new attribute containing a unique ID that exists solely for this purpose ...
A Universally Unique Identifier (UUID) is a 128-bit label used to uniquely identify objects in computer systems. The term Globally Unique Identifier (GUID) is also used, mostly in Microsoft systems. [1] [2] When generated according to the standard methods, UUIDs are, for practical purposes, unique.
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 database design, a persistent object identifier (POID) is a unique identifier of a record on a table, used as the primary key.Important characteristics of a POID are that it does not carry business information and are not generally exported or otherwise made visible to data users; as such a POID has many of the characteristics of a surrogate key.
The value must be greater than zero. A suitable value could be 1000 or 32767. There is a variable defined to hold the currently assigned high value and it is assigned the value 0 (zero). There is a variable defined to hold the currently assigned low value and it is assigned the value of the maximum low value plus 1 (one). The steps are:
I. IETF language tag; Industry Standard Coding Identification; Integrated Authority File; International Article Number; International Food Code; International Generic Sample Number