Rule Definition
The wider an index definition, the bigger the index becomes physically, and the more work the database has to perform when accessing or modifying the data. Because of this, you should avoid adding indexes to very wide columns. The narrower the index, the faster it will perform. You can't always avoid indexing wide columns or using composite indexes, but if you think you have to use one, be sure you have carefully evaluated your choice and are confident you don't have other options that may offer better performance.

Remediation
See rationale

Violation Code Sample

create table publishers
(
pub_id   char(45),
city        varchar(20),
state      char(2),
Constraint PK_publishers unique nonclustered
( pub_id asc  ) 
)