Sql primary key: integer vs varchar

sql

data-integrity

database-design

primary-keys

byNikita Barsukov·Nov 30, 2024

For optimal performance and memory efficiency, employ an integer as your SQL primary key. It beats the competition when it comes to indexing and joins, thanks to its smaller footprint and ability to auto-increment, guaranteeing uniqueness even on the busiest days.

Example:

/* Applying integer primary key like a boss */
CREATE TABLE Users (
  UserID INT PRIMARY KEY AUTO_INCREMENT, 
  UserName VARCHAR(255)
);

Comparisons involving integers are like greased lightning, turning large-scale database operations into pieces of cake. Conversely, varchars might give the database indigestion due to their larger meal size.

Key insights on surrogate keys

Surrogate keys have your back when it comes to data integrity and information security. These keys are conjured out of thin air (math, actually 😜), making them detached from the tangled web of business logic. This dodges the bullet of exposing sensitive business data, ensuring they remain as steady as a monument amidst the whirlwind of data changes. On the other side of the fence, natural keys may contain precious business data, but are not immune to the ravages of time.

Primary keys: Playing by the access patterns

Your database's access patterns are the alpha and omega in choosing the primary key. The width of the key carries as much weight as its data type in determining query performance. Nothing like a surrogate integer key to take the bull by the horns and usher in tidy disk storage and seamless data retrieval due to its fixed width.

Checking the domain-driven design box

Don't forget that your primary key pick should knock on the door of the domain model. The objective here is to shine the spotlight on fields that display a dogged persistence over time, ensuring they reaffirm their relevance in relation to the fundamental business context. The storage aspect, though important, doesn't tell the whole story; diving into the logical business model will keep your data's narrative integrity in a straight line.

Stability: The bedrock of key choices

Your primary keys should proudly wear the badges of the steadfast aspects of your database entities. Evade fields akin to shifting sands like the plague, lest they kick off update anomalies. Armed with immutable keys, your database design won't be a pushover.

Skirting the confirmation bias trap

The integer vs. varchar dispute is a minefield for confirmation bias. Strap on your detective glasses and conduct a meticulous investigation into your unique case, weigh the pros and cons, and lean towards the primary key choice that beams up the entity’s durability within the schema.

Making the case for surrogate keys

The inclusion of surrogate keys should stand its ground when pitted against the complexity they sprinkle on the logical model. The big question is: is there a clear advantage, or are we simply piling on the layers of abstraction?

When key changes seem inevitable

Tackling modification challenges head-on is a must for any primary key:

To handle historical tracking, lean on surrogate keys that keep history intact across changes.
To reconcile with external systems, natural keys with business data are your go-to choice.
Data correction? No problem. Surrogate keys ensure the train of data consistency leaves the station on time.

Varchar: A situational savior

When the stars align right, varchar primary keys claim the spotlight:

The span of possible values is small, fixed, and the cast is well-rehearsed.
The usage caters to performance perks woven into the cloth of existing access patterns.
The application ecosystem insists on a textual identifier (UUIDs, for instance).