SQL

psql fatal database does not exist

# So you do not have to create a database with your role name

psql -U Username DatabaseName 

fatal database postgres does not exist

psql -d template1

psql: error: FATAL: database "odoo" does not exist

# if your database is different as your login name you must add the database name
psql -U Username DatabaseName 

fatal database postgres does not exist

If the field is already a string, this will work

 SELECT RIGHT('000'+ISNULL(field,''),3)
If you want nulls to show as '000'

It might be an integer -- then you would want

 SELECT RIGHT('000'+CAST(field AS VARCHAR(3)),3)