A primary key is a column or set of columns in a database table that uniquely identify each row in the table. A unique key is a column or set of columns in a database table that can uniquely identify each row in the table, but which may contain NULL values.
What is Primary Key ?
In databases, a primary key is a unique identifier for a record. It can be either a single field or a combination of fields.
A primary key ensures that each record in a database is unique. By using a primary key, you can prevent duplicate records from being entered into the database.
A primary key also allows you to reference a record by using its primary key value. This can be useful when you want to update or delete a record.
What is Unique Key?
A unique key is a column or set of columns in a database table that can be used to uniquely identify each row in the table. A unique key can be a single column or a combination of columns. A unique key must contain unique values.
A primary key is a special type of unique key that is used to identify the primary record in a database table. A primary key must contain a unique value. A primary key can be either a single column or a combination of columns.
A foreign key is a column or set of columns in one database table that contains values that match the values in the primary key column or columns of another database table. Foreign keys are used to create relationships between tables.
Main differences between Primary Key and Unique Key
A primary key is a unique identifier for a given tuple in a table. A foreign key is a way to enforce referential integrity by linking two tables together. A unique key is an identifier for a given tuple in a table, but it does not have to be unique across tables.
A primary key must be unique within its own table, but it does not have to be unique across tables. A foreign key must be unique across tables, and it is used to link two tables together. A unique key may or may not be unique across tables, but it must be unique within its own table.
Similar Frequently Asked Questions (FAQ)
Why are they important?
A primary key is a column or set of columns in a database table that uniquely identify each row in the table. A unique key is a column or set of columns in a database table that can be used to uniquely identify each row in the table, but which may have some duplicate values.
In conclusion,it is important to understand the difference between a primary key and a unique key. A primary key is a column or set of columns that uniquely identify a row in a table.
Hey, I’m a blogger! I love to write about interesting things and I love to help people. I’ll be your go-to source for information on the newest trends in blogging, and how you can use them to improve your blog. Make sure to check out my blog for tips on how to make your blog better!