Should I Use Auto-Increments as Primary Keys in Relational Database Tables?

SQL: Creating a Relational Table with 2 Different Auto_increments

Understanding Auto_Increments and Relational Tables

In a true relational table, a column declared as a primary key is not automatically an auto-incremented ID.

Reasons for Avoiding Auto_Increments as Primary Key in Relational Tables:

• Non-unique: Auto-incremented IDs do not guarantee row uniqueness.
• Redundancy: Auto-incremented IDs are additional data that serve no purpose.
• Confusing Expectations: Treating auto-incremented IDs as primary keys leads to incorrect assumptions about row uniqueness and data integrity.

Creating a Relational Table without Auto_Increments

1. Define a Composite Primary Key: Create a primary key composed of columns that make up a unique identifier for each row.
2. Remove Unnecessary ID Fields: If an existing ID field was declared as a primary key, remove it and promote the composite primary key.
3. Ensure Row Uniqueness: Declare a unique constraint on the composite primary key to prevent duplicate rows.

Benefits of a Relational Table:

• Enforces row uniqueness for data integrity.
• Facilitates joins and queries based on the primary key.
• Improves performance by optimizing data access.

Example:

Consider the following relational table structure:

CREATE TABLE user (
    user_name VARCHAR(30) NOT NULL,
    name_first VARCHAR(30) NOT NULL,
    name_last VARCHAR(30) NOT NULL,
    PRIMARY KEY (user_name, name_first, name_last)
);

In this example, the primary key is composed of three columns, ensuring that each record represents a unique user. The absence of an auto-incremented ID column ensures that the table maintains row uniqueness without unnecessary overhead.

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