can we create database user name start with undercore(_) in aws Redshift?

 can we create database user name  start with underscore(_)  in aws Redshift?

No,its not allowed in IAM database user with Single sign on,you should create the database  name starting with character.

DbUser parameter must begin with a letter, contain only alphanumeric characters, underscore ('_'), plus sign ('+'), dot ('.'), at ('@'), or hyphen ('-'), and be less than 128 characters. (Service: AmazonRedshift; Status Code: 400; Error Code: InvalidParameterValue