What is the difference between Alternate Key and primary key?

Question

Primary key values should be unique and non-null. There can be multiple Super keys and Candidate keys in a table, but there can be only one Primary key in a table. Alternate keys are those Candidate keys that were not chosen to be the Primary key of the table.

What is the difference between Alternate Key and secondary key?

Alternate Key or Secondary Key is the key that has not been selected to be the primary key, but are candidate keys. However, it is considered a candidate key for the primary key. A candidate key not selected as a primary key is called alternate or secondary key.

What is an Alternate Key example?

For example, simply pressing A will type the letter 'a', but holding down the Alt key while pressing A will cause the computer to perform an Alt + A function, which varies from program to program. The international standard ISO/IEC 9995-2 calls it Alternate key.

Is Unique key and Alternate Key same?

Primary Key ==> Is used to uniquely identify records and doesn't allow NULL values. Unique Key ==> Is also used to uniquely identify records but does allow NULL Values per column combination. Alternate Key ==> Is another type of Unique key, which is used to identify each record uniquely. This is not a constraint.

What is Unique key and Alternate Key?

The remaining candidate keys are called unique keys because they can uniquely identify a record in a relation. Unique keys can consist of multiple columns. Unique keys are also called alternate keys. Unique keys are an alternative to the primary key of the relation.

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