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A unique key is comprised of a single column or a set of columns that can be used to uniquely identify a single row in a table. No two rows in a table can have the same non-Null value(s) in the column(s) that comprise the unique key. A table may have more than one unique key.
Example:
Suppose we have a table called "employees" in an employee database, and that table contains the following columns:
FirstName, LastName, EmployeeID, HireDate, SSN, DateOfBirth, Department, JobTitle
This table has at least two unique keys, EmployeeID and SSN (social security number) since both values are defined as being globally unique. In addition, {FirstName, LastName, EmployeeID} is also a unique key, as are any combination of columns that, when combined, exist in one and only one row in the table.
In this example, EmployeeID and SSN are both minimal unique keys. On their own, they each exist in one and only one row. Any unique key in a table can be the table's primary key. There is one and only one primary key in a table.
What else can I help you with?
What is the primary key field of a database?
its a unique key use to identify data in database
Why is a Key important in a database?
a key is important in a database because using of that key only we can identify a unique attribute.
What is meant by key in database?
A key is a unique part of the record that is used to index.
What does API key mean?
An API Key is an application programming interface. Inn smaller words it is how you can grab data from one website or database and use it on your website or database.
What is a field that has a unique value for each record in a database?
Primary key
Can you insert primary key only to one field in the database?
Yes. Primary key can be inserted to one field in the database. The field should be unique and not null.
Why is it necessary to have a primary key for each table of information of your database?
to have unique field
In a database files are called?
A database holds records in files that are called tables. Each table has a specific key that defines that table and each master key is unique.
What is the difference between primary key and secondary key in database?
The primary key is the field containing unique values that aid in database operations. The secondary key is used in addition or as an alternate to the primary key. Both are candidate keys, it's just that one was chosen to be primary.
What is concatenate key in a relational database?
The concatenate key is simply the combination of several columns in a table, which serves the unique key of that table.
What is used to unique identify each record in a database?
The "primary key" is the identifier that database systems use to identify a record uniquely.
What is a field that contains a unique value?
It can be referred to as a UNIQUE column. Such columns can be a:Primary KeyUnique Key orCandidate Keyin a database table
