Example Codes:

• Guaranteed Uniqueness: Across databases and systems, GUIDs ensure no collisions.
• Security: They don't reveal any sequential information about the data, unlike auto-incrementing integers.

• Performance: Larger size compared to integers, impacting storage and potentially slowing down queries that rely heavily on the primary key.
• Clustering: Using a GUID as a clustered index can fragment easily, further reducing performance.

Best Practices:

1. Use Auto-Incrementing Integer (INT/BIGINT) for Clustered Index:

• Set the primary key as an auto-incrementing integer for optimal performance in queries that join or filter based on the ID.
• This creates a compact clustered index that efficiently sorts and retrieves data.

1. GUID as a Separate Uniqueidentifier Column:

• Add a separate column with a GUID as a unique identifier.
• This provides uniqueness and security benefits without impacting performance on the clustered index.

1. Use NEWSEQUENTIALID() Function:

• If you must use a GUID as the primary key, consider using the NEWSEQUENTIALID() function in SQL Server.
• This generates GUIDs with a sequential component, improving clustered index performance compared to random GUIDs.
• Note: Server reboots can disrupt the sequential order.

1. Entity Framework Considerations:

• Entity Framework can handle both auto-incrementing integers and GUIDs as primary keys.
• If using a GUID, leverage code-first migrations to specify the desired approach (separate column or primary key).

Remember:

• Evaluate your specific needs. If uniqueness and security are paramount, a GUID might be worth the performance trade-off.
• Consider alternative approaches like sequences or database-generated identifiers if auto-incrementing integers don't meet your needs.

Example Codes:

CREATE TABLE Users (
  Id INT IDENTITY PRIMARY KEY,  -- Clustered index for efficient lookups
  UserId UNIQUEIDENTIFIER NOT NULL DEFAULT NEWSEQUENTIALID(),  -- Unique identifier
  Username VARCHAR(50) NOT NULL,
  ... other columns
);

Entity Framework (Code-First) - Separate GUID Column:

public class User
{
  public int Id { get; set; }  // Entity Framework will handle auto-increment
  public Guid UserId { get; set; } = Guid.NewGuid();  // Generate new GUID on creation
  public string Username { get; set; }
  // ... other properties
}

Entity Framework (Code-First) - GUID as Primary Key (consider performance implications):

public class Product
{
  public Guid ProductId { get; set; } = Guid.NewGuid();  // GUID as primary key
  public string Name { get; set; }
  // ... other properties
}

This is the most common and performant option for most scenarios. It offers:

• Smaller size: Saves storage space compared to a GUID.
• Faster queries: Enables efficient clustered index creation, leading to quicker data retrieval.
• Database Management: Most databases offer built-in functionality for auto-incrementing integers, simplifying implementation.

Sequences:

Sequences provide a way to generate unique, ordered identifiers within a database. They offer:

• Control over Order: Unlike auto-incrementing integers, sequences allow you to define the increment value and starting point.
• Portability: Sequences are often supported across different database platforms, making your code more portable.

Database-Generated Identifiers:

Some databases offer built-in functions to generate unique identifiers. This can be:

• Vendor-Specific: The syntax and functionality might differ between database platforms.
• Similar to Auto-Incrementing Integers: They typically provide unique, ordered values, similar to auto-incrementing integers.

Choosing the Right Method:

• Go with auto-incrementing integers for most cases. It's efficient, widely supported, and avoids the overhead of GUIDs.
• Consider sequences if you need to control the order of identifiers or for portability across databases.
• Explore database-generated identifiers if your database offers a convenient way to generate unique values.