log/what is surogate key
What is it?
A surrogate key in a database is a unique identifier for either an "entity" in the modeled world or an "object" in the database. The surrogate key is "not" derived from application data.
Surrogate keys serve as unique identifiers within a database, replacing natural keys when they are unsuitable for creating a unique primary key. They offer stability, as they remain unchanged throughout the lifespan of a row, and adaptability, as they are unaffected by changes in the source system, such as migrations.
Their numeric nature enhances performance in data processing and queries, and their uniformity across tables streamlines the Extract, Transform, Load (ETL) process. In practical applications, such as in telecommunications, surrogate keys facilitate the management of data from multiple sources by assigning unique incremental values to each record, even when the records originate from different systems.
This approach allows for separate data handling while enabling aggregated analysis at a higher level, ensuring that data integrity and reporting accuracy are maintained.
Difference with Primary Key
Imagine you have a group of people waiting in line to enter a building, and each person has a unique identifier card.
- Primary Key:
- Think of the primary key as a person's ID card.
- Each person has a unique ID card that helps identify them in the line.
- The ID card might have information like the person's name, date of birth, or other relevant details.
- When you want to find or refer to a specific person in the line, you use their ID card to locate them.
- The ID card is essential for ensuring each person is unique and identifiable within the line.
- Surrogate Key:
- Now, think of the surrogate key as a numbered token given to each person in the line.
- These tokens are not related to any personal information or characteristics of the people in the line.
- Instead, they're just sequential numbers (like 1, 2, 3, ...) or randomly generated codes.
- Each person holds their token while waiting in line.
- When you want to refer to a specific person in the line, you don't need to know anything about them personally; you just need their token number.
- These tokens are only used to manage the line efficiently and aren't tied to any specific attributes of the individuals.
In this analogy, the primary key (ID card) is based on personal information and helps uniquely identify each person, while the surrogate key (numbered token) is a system-generated identifier used solely for managing the line and doesn't carry any inherent meaning about the people in it.
