The spelling of the word "alternate key" can be explained using the International Phonetic Alphabet (IPA) phonetic transcription. The first syllable "al-" is pronounced as /ˈæl/ with a short "a" sound. The second syllable "-ter-" is pronounced as /ˈtɜːr/ with a long "e" sound. The third syllable "-nate" is pronounced as /neɪt/, with a long "a" sound. The final syllable "-key" is pronounced as /ki/ with a short "i" sound. Together, they form the word /ˈæltəneɪt ki/. An alternate key is a secondary key that can be used for accessing a computer system, often used as a backup in case the primary key fails.
An alternate key, in the context of relational databases, is a candidate key that has not been designated as the primary key. It is a unique identifier for a record within a table, just like a primary key, but it serves as an alternative option for identifying and accessing data.
Typically, a table in a database can have multiple candidate keys, and each of these keys can function as an alternate key. However, only one of them is chosen as the primary key, which is used to uniquely identify each record in the table. The remaining candidate keys become alternate keys, providing additional means for referencing and retrieving data.
Unlike the primary key, the alternate key does not necessarily need to be unique across the entire table. It may allow duplicate values within the context of the column it belongs to. However, it should still possess the property of uniqueness within its own column, enabling it to unequivocally identify records when used as a reference.
The purpose of having alternate keys is to allow for flexibility in querying and accessing data. In some cases, alternate keys may also be used for enforcing data integrity and ensuring the accuracy and consistency of the information stored in the database.
In summary, an alternate key is a candidate key within a table that serves as an alternative means of uniquely identifying records, different from the primary key. It provides additional options for accessing and retrieving data, aiding in database management and query flexibility.
The word "alternate" comes from the Latin word "alternatus", which means "to do by turns" or "to interchange". The word "key" refers to a means of accessing or unlocking something. In the context of databases and computer systems, an "alternate key" is a term used to describe a unique identifier that can be used in place of the primary key to access or locate specific data records. Therefore, the term "alternate key" combines the idea of interchanging or substituting with a means of access or identification.