How many alternate keys can be there in a table?

Question

There can be one or more alternate keys in a table and contain NULL values unless it is mentioned to be NOT NULL explicitly. The UNIQUE keyword is used to define the alternate key, which indicates the value must be unique.

Can a table have multiple alternate keys?

A table can have multiple candidate keys. One of them is specified as Primary key and rest of them can be called as alternate key. Alternate key: There can be more than one keys which can identify each row of the table uniquely.

What is alternate keys in table?

ALTERNATE KEYS is a column or group of columns in a table that uniquely identify every row in that table. A table can have multiple choices for a primary key but only one can be set as the primary key. All the keys which are not primary key are called an Alternate Key.

Is there any alternate key in table student?

Let's take an example of student it can contain NAME, ROLL NO., ID and CLASS. Here ROLL NO. is primary key and rest of all columns like NAME, ID and CLASS are alternate keys. If a table has more than one candidate key, one of them will become the primary key and rest of all are called alternate keys.

Can a primary key be alternate key?

A Primary Key can't be an Alternate Key. For a table with a single Candidate Key which has to be the Primary Key will not contain any Alternate Key. A Foreign Key can't be an Alternate Key as it is only used to reference another table. The alternate Key should be unique.

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