What is a secondary key example?

What is a secondary key used for?

A secondary key shows the secondary value that is unique for each record. It can be used to identify the record and it is usually indexed. It is also termed as Alternate key. A table may have a primary key that is system generated and a secondary key that comes from the sources and other processes.

How many secondary keys are there?

You can use a maximum of 16 distinct fields to define a primary key. The number of fields used in the primary key limits the number of fields in the secondary keys. Fields used by one key can also be used in another key; however, no more than 16 unique fields can be used to create primary or secondary keys.

What is secondary key in ER diagram?

A secondary key is used strictly for retrieval purposes and accessing records [5]. These keys do not have to be unique and are typically not included in an E-R diagram. The term secondary key is also occasionally used as a synonym for alternate key [6].

Is secondary key and foreign key same?

That country column in the customer table would be a foreign key. A secondary key on the other hand is just a different column in the table that you have used to create an index (which is used to speed up queries). Foreign keys have nothing to do with improving query speeds.