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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 .
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.
A non-primary key that can be used to identify only one row in a table. Alternate keys may be used like a primary key in a single-table select. Foreign. A key that has migrated to another entity. At the most basic definition, "a key is a unique identifier", [1] so unique key is a pleonasm.
Universally unique identifier. A Universally Unique Identifier ( UUID) is a 128-bit label used for information 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.
Primary keys can be an integer that is incremented, a universally unique identifier (UUID) or can be generated using Hi/Lo algorithm. Defining primary keys in SQL. Primary keys are defined in the ISO SQL Standard, through the PRIMARY KEY constraint. The syntax to add such a constraint to an existing table is defined in SQL:2003 like this:
Structured Query Language ( SQL) ( pronounced S-Q-L; historically "sequel") [4] [5] is a domain-specific language used to manage data, especially in a relational database management system (RDBMS). It is particularly useful in handling structured data, i.e., data incorporating relations among entities and variables.
Persistent object identifier. 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 ...
Superkey. In the relational data model a superkey is any set of attributes that uniquely identifies each tuple of a relation. [1] [2] Because superkey values are unique, tuples with the same superkey value must also have the same non-key attribute values. That is, non-key attributes are functionally dependent on the superkey.