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Table of contents
1.
Introduction
2.
What is a Surrogate Key?
2.1.
Why Use a Surrogate Key?
3.
Creating a Surrogate Key in SQL
4.
Frequently Asked Questions
4.1.
Is a Surrogate Key always an integer?
4.2.
Can a table have more than one Surrogate Key?
4.3.
Does a Surrogate Key have business meaning?
5.
Conclusion
Last Updated: Mar 27, 2024
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SURROGATE Key in SQL

Author Gunjan Batra
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Introduction

In the world of databases, keys play a vital role in linking and identifying data across tables. One such key is a Surrogate Key, a concept often used in SQL databases.

Surrogate Key in SQL

 In this article, we'll delve into what Surrogate Keys are, why they're used, and how to create them in SQL.

What is a Surrogate Key?

A Surrogate Key is a unique, system-generated identifier used as the primary key in a table. It's not derived from the data in the table and usually has no meaningful business value. Surrogate keys are often integers, but they can also be other data types, such as sequential unique identifiers (UUIDs).

Why Use a Surrogate Key?

The main reasons to use Surrogate Keys are simplicity, performance, and stability. They're simple because they're often just incrementing integers, meaning they're easy to manage and understand. They offer good performance, especially in large databases, because comparing integers is usually faster than comparing other data types. Finally, they provide stability because they don't change, even if other data in the row changes.

Creating a Surrogate Key in SQL

In Sql, creating a Surrogate Key usually involves creating an auto-incrementing integer field. In MySQL, this can be done as follows:

CREATE TABLE Customers (
    CustomerID int NOT NULL AUTO_INCREMENT,
    CustomerName varchar(255) NOT NULL,
    ContactName varchar(255),
    Country varchar(255),
    PRIMARY KEY (CustomerID)
);
output

In this SQL statement, CustomerID is a Surrogate Key. It's an integer and is set to auto-increment every time a new record is added, ensuring its uniqueness across the Customers table.

Frequently Asked Questions

Is a Surrogate Key always an integer?

No, while it's common for Surrogate Keys to be integers, they can also be other data types, such as UUIDs.

Can a table have more than one Surrogate Key?

Typically, a table will only have one Surrogate Key, which acts as the primary key.

Does a Surrogate Key have business meaning?

No, Surrogate Keys are system-generated and typically don't have any business meaning.

Conclusion

Understanding Surrogate Keys is crucial when working with SQL databases. They provide a simple, efficient, and stable way to uniquely identify records in a table, making them a valuable tool in any database developer's toolkit.

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