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In Database Management Systems (DBMS), the concept of surrogate keys plays an important role in ensuring efficient data management and retrieval. A surrogate key in DBMS is a unique identifier assigned to each record in a table to serve as the primary key.
A surrogate key in DBMS is a system-generated identifier. It is used as a primary key for a table. Unlike Natural keys, which are based on existing data attributes in a table, surrogate keys are generated using a sequence, a random number generator, or other algorithms. Surrogate keys are used in database design to provide a reliable and unique primary key for a table when no suitable natural key is available, or the natural key is too complex.
Let’s look at an example for better understanding. Here's an example of a driver table with a surrogate key:
CREATE TABLE driver (
driver_id INT NOT NULL AUTO_INCREMENT,
name VARCHAR(50) NOT NULL,
address VARCHAR(100) NOT NULL,
phone VARCHAR(20),
email VARCHAR(100) NOT NULL,
PRIMARY KEY (driver_id)
);
Features of the Surrogate Key
Some of the features of the surrogate key are given below:
Uniqueness: The surrogate key is always unique for each record in a table, regardless of the stored data in the table.
Simplicity: Surrogate keys such as a GUID(Globally Unique Identifier), a sequential number, or a random number can be generated easily.
Stability:Surrogate keys are undoubtedly stable and do not change over time, even after the values they represent are changed. This makes surrogate keys ideal for referencing records in other tables.
Efficiency: Surrogate keys are smaller and faster. Natural keys, which are complex, long, or inefficient, are used for database index, query, and reference records.
Independence: Surrogate keys are independent of data values in a table. Surrogate keys can also be used when the natural key is not available or when the natural key is complex, long, volatile, or inefficient to use.
Example:
An auto-incremented numeric value generated for each record, ensuring unique identification without relying on the inherent properties of the data.
A surrogate key assigned to an employee ID, unaffected by changes in personal details like name or department, providing stability in database relationships.
Why use a Surrogate Key in DBMS?
Utilizing surrogate keys in Database Management Systems (DBMS) offers several advantages that enhance data management and system efficiency. Surrogate keys ensure the uniqueness of each record, mitigating the risk of duplicates and maintaining robust data integrity. Their stability is crucial, as surrogate keys remain constant over time, providing a reliable reference even when natural keys undergo changes.
Importantly, surrogate keys are designed to be meaningless, reducing the complexities associated with using natural keys and establishing a consistent and reliable identification system. This simplicity extends to data management, especially in tables with intricate or composite keys, where surrogate keys provide a straightforward and standardized approach to uniquely identifying records.
Implementing Surrogate Key
Implementing a surrogate key in a DBMS involves the following steps; let’s learn how to implement a surrogate key:
Finding the table that requires a key: The first step is to determine the table that requires a surrogate key. This could be a new table or an existing table.
Pick a method for generating keys:After determining the table which requires a key, the next step is to choose a method for generating surrogate keys. Sequence, a random number generator, or an algorithm are some common methods.
Addition of a new column:After determining and choosing the method, the controlfurther step is to add a new column to the table to store the surrogate key. This column should be set as the primary key for the table.
Generate the surrogate key values:The further step is to generate a unique surrogate key value for each record in the table. By using SQL queries or through a built-in function in the DBMS, can key generate.
Test the implementation:The final step after the surrogate key has been added and updated, test the implementation and ensure that it is working correctly.
Example
Creates a table named Customer
-- Creating table with name Customer.
CREATE TABLE [dbo].[Customer](
[Id] [int] IDENTITY(1,1) PRIMARY KEY,
[Name] [varchar](15) NULL,
[SSN] [varchar](11) NULL,
[Email] [varchar](25) NULL,
);
-- Inserting values into the table.
INSERT INTO [dbo].[Customer] VALUES ('Ninja1', '123-45-6789', 'Ninja1@codingninja.com');
INSERT INTO [dbo].[Employee] VALUES ('Ninja2','998-76-5432', 'Ninja2@codingninja.com');
INSERT INTO [dbo].[Employee] VALUES ('Ninja3', '880-98-3456', 'Ninja3@codingninja.com');
GO
--Printing values form the table.
SELECT * FROM [dbo].[Customer];
GO
Output
How to Create the SURROGATE Key in SQL?
In SQL, a surrogate key is a unique identifier assigned to each record in a table to ensure that each row can be uniquely identified. Surrogate keys are typically integer values generated automatically by the database management system (DBMS) and have no inherent meaning or significance outside the database context.
To create a surrogate key in SQL, you can follow these steps:
Choose the Data Type: Decide on the appropriate data type for the surrogate key. Integer data types like INT or BIGINT are commonly used for surrogate keys due to their efficiency and ability to handle large ranges of values.
Define the Surrogate Key Column: Add a new column to the table that will serve as the surrogate key. This column should be defined with the chosen data type and designated as the primary key or a unique constraint to enforce uniqueness.
Auto-Generate Values: Utilize the auto-increment or identity feature provided by the database system to automatically generate unique values for the surrogate key column. This ensures that each new record inserted into the table will be assigned a unique surrogate key value without requiring manual intervention.
Ensure Uniqueness: Ensure that the surrogate key column maintains its uniqueness constraint by enforcing primary key or unique constraints on the column. This prevents duplicate values from being inserted and maintains the integrity of the surrogate key.
How Can We Use a SURROGATE Key in SQL?
In SQL, a surrogate key serves as a unique identifier for each record in a table, providing a reliable means of referencing and retrieving specific data. Here's how we can effectively utilize surrogate keys in SQL:
Primary Key: Surrogate keys are commonly used as primary keys for tables. By designating the surrogate key column as the primary key, you ensure that each record has a unique identifier and enforce data integrity constraints.
Foreign Key References: Surrogate keys can be referenced by foreign key constraints in related tables to establish relationships between entities. This allows for efficient data retrieval through joins and ensures referential integrity across multiple tables.
Data Modification: Surrogate keys facilitate seamless data modification operations such as updates and deletions. Since surrogate keys have no inherent meaning, they can be changed without affecting the semantics of the data, unlike natural keys.
Performance Optimization: Surrogate keys can improve database performance by providing a compact and efficient means of indexing records. Indexes created on surrogate key columns enable fast data retrieval operations, especially for large datasets.
Integration with ORMs: Object-relational mapping (ORM) frameworks commonly rely on surrogate keys to map database entities to application objects. Surrogate keys simplify object identification and mapping, enhancing the development and maintenance of database-driven applications.
Advantages of Surrogate Key
Surrogate keys in DBMS provide several advantages. Some of them are the following:
Uniqueness: Surrogate keys are generated using different methods, ensuring that the record in the table has a unique identifier. This advantage of the surrogate key helps in no duplicate entries.
Stability: Surrogate keys are designed to be stable. This makes surrogate keys ideal for referencing records in other tables. There are a few ways by which surrogate keys can improve data stability:
Stability of data relationships.
Stable primary key.
Avoids data duplication.
Simplifies data updates.
3. Performance: Surrogate keys are smaller and simpler than natural keys. Due to this reason, surrogate keys are faster to use for index, search, and query purposes. This improves the performance of the database.
4. Flexibility: The surrogate key is used in a wide variety of applications independent of the structure of the stored data. This makes the surrogate key worthwhile when complex, multi-faceted data exists.
5. Security: Surrogate keys protect sensitive data as they act as identifiers. Due to this advantage of surrogate keys, users can access the data they need while maintaining strict access control and security policies.
Disadvantages of surrogate key
Surrogate keys in DBMS provide many benefits, but they also have some disadvantages. Let’s learn about the disadvantages of the surrogate key in DBMS:
Extra storage: Using surrogate keys requires adding an additional column to the table. Adding a new column also adds to the storage requirements of the database.
Complexity: Surrogate keys are a very useful tool in DBMS but this key also has disadvantages while using them. Surrogate keys added complexity. This complexity can arise in different ways:
Loss of meaning
Maintenance
Additional column
Join complexity
3. Lack of Meaning: Surrogate keys have no meaning to users. Surrogate keys do not relate to real-world data. This makes it difficult to understand the relationship between tables in the database.
4. Inefficiency: Surrogate keys can result in inefficiency for some cases, like querying and joining tables. Especially when surrogate keys are not in sequential order or not used as the clustered index.
5. Maintenance: Surrogate keys can be time-consuming and complex to manage. This is because it ensures that the key is unique and correct.
Natural Key vs Surrogate Key vs Composite Key
Let’s have a look at the following difference between Primary key and surrogate keys:
Parameters
Natural Key
Surrogate Key
Composite Key
Definition
A natural key is a key composed of attributes that already exist naturally in the data and have inherent meaning or significance.
A surrogate key is an artificial key generated by the database system to uniquely identify each record in a table.
A composite key is a key that consists of multiple columns combined to uniquely identify a record.
Meaning
Natural keys have inherent meaning and may represent real-world attributes or properties.
Surrogate keys have no inherent meaning or significance outside the database context.
Composite keys may or may not have inherent meaning depending on the combination of attributes used.
Source of Values
Natural keys are derived from existing attributes in the data model and are often chosen based on their uniqueness and semantic relevance.
Surrogate keys are typically auto-generated by the database system, often as sequential integers.
Composite keys are composed of values from multiple attributes within the same table.
Usage
Natural keys are commonly used when there is a unique and meaningful attribute or combination of attributes that can uniquely identify records.
Surrogate keys are used when there is no suitable natural key or when data needs to be anonymized or obfuscated.
Composite keys are used when a single attribute is insufficient to uniquely identify a record, requiring a combination of attributes.
Stability
Natural keys may change over time if the underlying attributes change, potentially impacting data integrity.
Surrogate keys are typically stable and rarely change over time.
Composite keys may change over time if any of the component attributes change, impacting data consistency.
Performance
Natural keys may offer good performance due to their inherent meaning and relevance to the data model.
Surrogate keys can improve performance in terms of indexing and data retrieval due to their sequential and compact nature.
Composite keys may offer good performance if the combination of attributes is well-selected and efficiently indexed.
A surrogate key is a unique identifier generated by the database system for the purpose of uniquely identifying each record in a table.
A primary key is a unique identifier that uniquely identifies each record in a table and is chosen from among existing candidate keys.
Meaning
Surrogate keys have no inherent meaning or significance outside the database context.
Primary keys may have inherent meaning and can be derived from attributes that have semantic relevance.
Source of Values
Surrogate keys are typically auto-generated by the database system, often as sequential integers.
Primary keys are chosen from existing attributes or candidate keys based on their uniqueness and relevance to the data model.
Usage
Surrogate keys are commonly used in situations where there is no suitable natural key or when data needs to be anonymized or obfuscated.
Primary keys are essential for maintaining data integrity and enforcing entity integrity constraints. They are fundamental for establishing relationships between tables and ensuring data consistency.
Stability
Surrogate keys are typically stable and rarely change over time.
Primary keys may change if the underlying attributes or candidate keys change, impacting data consistency.
Performance
Surrogate keys can improve performance in terms of indexing and data retrieval due to their sequential and compact nature.
Primary keys may offer slightly better performance compared to surrogate keys in some cases, especially when natural keys are used.
Frequently Asked Questions
What is another name for surrogate key?
Another name for a surrogate key is a "synthetic key." A synthetic key is an artificial identifier generated by the database management system (DBMS) to uniquely identify each record in a table. Unlike natural keys, which are derived from existing attributes with inherent meaning or significance, synthetic keys have no inherent meaning outside the database context.
Why do we use surrogate keys in DBMS?
Surrogate keys provide a unique identifier for each record in a table and ensure data integrity and referential integrity between tables.
How is the surrogate key in DBMS generated?
Surrogate keys can be generated using a variety of methods, including sequences, random number generators, or other algorithms.
Can surrogate key be null?
Yes, a surrogate key can be null, although it's uncommon. It is typically used when the actual value is unknown or undefined.
Conclusion
In this article, we have discussed about the surrogate key in DBMS. The adoption of surrogate key in DBMS stands as a strategic choice, providing a range of benefits for efficient and reliable data management. The unique, stable, and meaningless nature of surrogate keys enhances data integrity, simplifies system complexity, and contributes to improved performance. You can also find out some related articles on our platform like:
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