What are the solutions to database primary key conflicts?

Database primary key conflicts occur when two or more records attempt to use the same primary key value, which must be unique within a table. Here are several solutions to handle primary key conflicts:

1. Unique Constraints

Ensure that the primary key column has a unique constraint. This prevents any duplicate entries from being inserted.

Example: In a table named Employees, the EmployeeID column is set as the primary key. Any attempt to insert a record with an existing EmployeeID will result in a conflict error.

2. Auto-Increment Fields

Use auto-increment fields for primary keys. This ensures each new record automatically receives a unique identifier.

Example: In MySQL, you can define an auto-increment primary key like this:

CREATE TABLE Employees (
    EmployeeID INT AUTO_INCREMENT PRIMARY KEY,
    Name VARCHAR(100)
);

3. UUIDs (Universally Unique Identifiers)

Use UUIDs for primary keys. UUIDs are 128-bit values that are almost guaranteed to be unique across different systems and databases.

Example: In PostgreSQL, you can generate a UUID primary key using the uuid-ossp extension:

CREATE EXTENSION IF NOT EXISTS "uuid-ossp";
CREATE TABLE Employees (
    EmployeeID UUID PRIMARY KEY DEFAULT uuid_generate_v4(),
    Name VARCHAR(100)
);

4. Composite Primary Keys

Use a combination of columns to create a composite primary key, ensuring uniqueness across multiple fields.

Example: In a table named OrderDetails, you might use a composite primary key consisting of OrderID and ProductID:

CREATE TABLE OrderDetails (
    OrderID INT,
    ProductID INT,
    Quantity INT,
    PRIMARY KEY (OrderID, ProductID)
);

5. Conflict Resolution Strategies in Distributed Systems

In distributed databases or cloud environments, where data might be replicated across multiple nodes, conflict resolution strategies like last-write-wins, custom business logic, or consensus algorithms (e.g., Paxos, Raft) can be employed.

Example: Tencent Cloud's Distributed Database Service (TDSQL) offers features to handle conflicts in distributed environments, ensuring data consistency and availability.

6. Manual Intervention

In some cases, manual intervention might be required to resolve conflicts, especially when dealing with legacy systems or complex data migration scenarios.

Example: An administrator might need to review conflicting records and decide which one to keep or manually modify the primary key values to ensure uniqueness.

By implementing these solutions, you can effectively manage and prevent primary key conflicts in your databases, ensuring data integrity and system reliability.