What is alternate key example?

What is an alternative key example?

An alternate key is a key associated with one or more columns whose values ​​uniquely identify each row in the table, but which is not the primary key. For example, if the primary key of a table could be the employee ID, the alternate key could combine the employee’s first name, middle name, and last name.

What is an alternate key?

Alternate key or secondary key is the key that has not been chosen as primary key but are candidate keys. However, it is considered a candidate key for the primary key. A candidate key not selected as the primary key is referred to as an alternate key or secondary key.

What is the alternate key for?

Using an alternate key An alternate key is just a candidate key, so the use/role of an alternate key is the same. This means that an alternate key is also used to identify columns in a table that can uniquely identify all records in the table.

What do you mean by alternate key in a table, provide a suitable example of an alternate key from a table that contains meaningful data?

Provide an appropriate example of key candidates from a table of meaningful data. Answer: Candidate Key: A candidate key is a key that can uniquely identify each row of a table. … If the table has more than one candidate key, one of them becomes the primary key and the others are called alternate keys.

What is a candidate key with example?

Candidate Key: The minimal set of attributes that can uniquely identify a tuple is called a candidate key. Example: STUD_NO in the STUDENT relationship. The candidate key value is unique for each tuple and is not null. There can be more than one candidate key in a relation.

What is the difference between primary key and alternate key?

Primary key values ​​must be unique and not null. A table can contain multiple super keys and candidate keys, but there can only be one primary key in a table. Alternate keys are candidate keys that have not been selected as the table’s primary key.

Do alternative key values ​​have to be unique?

Alternate key values ​​must be unique. If a table consists of only one candidate key, that becomes the primary key; there is no alternate key.

When you define a table’s primary key, the DBMS automatically creates ?

If a primary key is defined on the table, the DBMS automatically creates a unique index on a primary key column. Indexes play an important role in DBMS implementation of primary keys. When you define a table’s primary key, the DBMS automatically creates a unique index on the primary key column you declare.

What kind of key consists of multiple fields?

A composite key consists of multiple fields to uniquely identify a record.

Can the foreign key be null?

Short answer: Yes, it can be NULL or double. I want to explain why a foreign key might need to be null or unique or not unique. First, remember that a foreign key simply requires that the value of that field first exist in another table (the parent table). … By definition, zero is not a value.

Is the candidate key the same as the primary key?

The primary key is a unique, non-null key that uniquely identifies a record in the table. A table can only have one primary key. The candidate key is also a unique key to uniquely identify a record in a table, but a table can have multiple candidate keys.