It's an arbitrary but common one used in SQL Server. If the example used 128, you'd ask "why 128?" If it was 64, 50, 100, or any other number, you'd still ask.

It's an arbitrary but common one used in SQL Server. If the example used 128, you'd ask "why 128?" If it was 64, 50, 100, or any other number, you'd still ask. What is the right number? String lengths should come from business rules and the data domain but, when those don't exist (or someone is creating a fake table just to show an example), they borrow from other examples or existing schemas. It's clearly not the point of the article to come up with the absolute best and universally satisfying table design for orders.