What is Hibernate Query Language (HQL)?
Hibernate query language, a query language follows the SQL. HQL is fully object-oriented and it supports inheritance, polymorphism, abstraction. Queries in HQL are case-insensitive excluding the name of classes of java and the properties.
For reading more about HQL please go through the link below may, this will be helpful for you.
For reading more about various clauses, queries, functions please go through the link