Key field
Encyclopedia
A key field is a field or set of fields (a key is then said to be a composite key) of a database
(typically a relational database
) table which together form a unique identifier
for a database record (a table entry). The aggregate of these fields is usually referred to simply as "the key". Key fields also define searches. Relational database
s enforce referential integrity
of their tables by matching primary keys with foreign keys. Keys can also be distinguished in technical keys (also known as surrogate key
s) and business keys (also known as natural key
s or domain keys).
Sometimes programmers embed a list of key values in a non-key character string fields. Many times the values in these fields cannot be guaranteed since no database can enforce the integrity of these values.
Also see primary key and foreign key
.
Database
A database is an organized collection of data for one or more purposes, usually in digital form. The data are typically organized to model relevant aspects of reality , in a way that supports processes requiring this information...
(typically a relational database
Relational database
A relational database is a database that conforms to relational model theory. The software used in a relational database is called a relational database management system . Colloquial use of the term "relational database" may refer to the RDBMS software, or the relational database itself...
) table which together form a unique identifier
Unique identifier
With reference to a given set of objects, a unique identifier is any identifier which is guaranteed to be unique among all identifiers used for those objects and for a specific purpose...
for a database record (a table entry). The aggregate of these fields is usually referred to simply as "the key". Key fields also define searches. Relational database
Relational database
A relational database is a database that conforms to relational model theory. The software used in a relational database is called a relational database management system . Colloquial use of the term "relational database" may refer to the RDBMS software, or the relational database itself...
s enforce referential integrity
Referential integrity
Referential integrity is a property of data which, when satisfied, requires every value of one attribute of a relation to exist as a value of another attribute in a different relation ....
of their tables by matching primary keys with foreign keys. Keys can also be distinguished in technical keys (also known as surrogate key
Surrogate key
A surrogate key 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.- Definition :There are at least two definitions of a surrogate:...
s) and business keys (also known as natural key
Natural key
In relational model database design, a natural key is a candidate key that has a logical relationship to the attributes within that row. A natural key is sometimes called a domain key.The main advantage of a natural key over a surrogate key, which has no...
s or domain keys).
Sometimes programmers embed a list of key values in a non-key character string fields. Many times the values in these fields cannot be guaranteed since no database can enforce the integrity of these values.
Also see primary key and foreign key
Foreign key
In the context of relational databases, a foreign key is a referential constraint between two tables.A foreign key is a field in a relational table that matches a candidate key of another table...
.