Raw expressions are the qb escape hatch. While qb strives to provide ways to execute the majority of queries, you will occasionally need to provide raw sql values that are not processed by qb. These SQL snippets are called raw or Expressions in qb.
raw expressions are useful, but shoud be used only if there is not another way to accomplish the same action using other qb methods. This is because a raw expression has the potential to use syntax specific to one database grammar or another, preventing you from easily switching from one grammar to another, one of the major benefits of using qb.
The first way to retrieve an Expression is to call the raw method on the QueryBuilder object.
The raw sql to wrap up in an Expression.
The sql snippet passed to raw is not processed by qb at all. With that in mind, it is important to follow all best practices and security recommendations with the sql you use with raw.