What is natural and surrogate key?

What is surrogate key?

A surrogate key is a unique key for an entity in the client's business or for an object in the database. Sometimes natural keys cannot be used to create a unique primary key of the table. This is when the data modeler or architect decides to use surrogate or helping keys for a table in the LDM.

What is a natural key in database?

A natural key is a column or set of columns that already exist in the table (e.g. they are attributes of the entity within the data model) and uniquely identify a record in the table. Since these columns are attributes of the entity they obviously have business meaning.

What is a surrogate key in SQL?

A surrogate key in SQL Server is created a by assigning an identity property to a column that has a number data type. A surrogate key is a value generated right before the record is inserted into a table. There are several reasons to replace a natural key with a surrogate key.

What is natural key in Oracle?

a natural key is an immutable set of attributes that uniquely identify a row that occur naturally with the row itself. a surrogate key is an immutable set of attributes that uniquely identify a row that were generated specifically and soley to identify this row (they did not occur naturally)