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⭐ Core Definition: Primary key

In the relational model of databases, a primary key is a designated set of attributes (column(s)) 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 surrogate key).

Examples of natural keys that could be suitable primary keys include data that is already by definition unique to all items in the table such as a national identification number attribute for person records, or the combination of a very precise timestamp attribute with a very precise location attribute for event records.

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👉 Primary key in the context of Numbering scheme

There are many different numbering schemes for assigning nominal numbers to entities. These generally require an agreed set of rules, or a central coordinator. The schemes can be considered to be examples of a primary key of a database management system table, whose table definitions require a database design.

In computability theory, the simplest numbering scheme is the assignment of natural numbers to a set of objects such as functions, rational numbers, graphs, or words in some formal language. A numbering can be used to transfer the idea of computability and related concepts, which are originally defined on the natural numbers using computable functions, to these different types of objects.

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⭐ Core Definition: Primary key
👉 Primary key in the context of Numbering scheme
Primary key in the context of Table (database)
Primary key in the context of Unique identifier

Primary key in the context of Table (database)

In a database, a table is a collection of related data organized in table format; consisting of columns and rows.

In relational databases, and flat file databases, a table is a set of data elements (values) using a model of vertical columns (identifiable by name) and horizontal rows, the cell being the unit where a row and column intersect. A table has a specified number of columns, but can have any number of rows. Each row is identified by one or more values appearing in a particular column subset. A specific choice of columns which uniquely identify rows is called the primary key.

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Primary key in the context of 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. The concept was formalized early in the development of computer science and information systems. In general, it was associated with an atomic data type.

In relational databases, certain attributes of an entity that serve as unique identifiers are called primary keys.In mathematics, set theory uses the concept of element indices as unique identifiers.

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Primary key in the context of "Numbering scheme"

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⭐ Core Definition: Primary key

👉 Primary key in the context of Numbering scheme

Primary key in the context of Table (database)

Primary key in the context of Unique identifier