They say UML is the best way to design databases is that right? if no what is the best?

ERD is the main for designing fatabases. With ERD anyone can create the databases (tools are available).

It also helps to reverse engineer an existing database into a model using either relational or object relational modeling concepts.

The Unified Modeling Language –UML- is OMG’s most-used specification. UML is a de facto standard for object modeling, and it is often used for database design as well. But how good is UML really for the task of database conceptual modeling? The truth is that UML is not good for designing database

UML is a modeling notation and is used to describe system structure and behavior; it uses a number of diagrams of which package, class, use case and sequence are most popular. Some case tools extend UML and can be used for data base design and SQL generation.

ERD is best used for database design.

No, UML [Unified Modeling Language] is used mainly for designing OOP applications,

ERD [Entity Relationship Diagram] is the main, popular and right way to design databases

if you use OOAD methodology you can use  class diagram to build application entities and set the relations between entities. then you can generate your tables from class diagram entities based on this artical

http://www.ibm.com/developerworks/library/ws-mapping-to-rdb/

ERP is the tool to document your design, but it will not let you design. Designing database will depends on user requirements, and system architecture.