SQL is a powerful and highly expressive language for queries against relational databases. SQL is established, standardised and hardly challenged by alternative querying languages. Nonetheless, in the Java ecosystem, there had been few relevant steps forward since JDBC to better integrate SQL into Java. All attention was given to object-relational mapping and language abstractions on a higher level, such as OQL, HQL, JPQL, CriteriaQuery. In the mean time, these abstractions have become almost as complex as SQL itself, regardless of the headaches they're giving to DBAs who can no longer patch the generated SQL.
jOOQ is a dual-licensed Open Source product filling this gap. It implements SQL itself as an internal domain-specific language in Java, allowing for the typesafe construction and execution of SQL statements of arbitrary complexity. This includes nested selects, derived tables, joins, semi-joins, anti-joins, self-joins, aliasing, as well as many vendor-specific extensions such as stored procedures, arrays, user-defined types, recursive SQL, grouping sets, pivot tables, window functions and many other OLAP features. jOOQ also includes a source code generator allowing you to compile queries in modern IDEs such as Eclipse very efficiently.
jOOQ is a good choice in a Java application where SQL and the specific relational database are important. It is an alternative when JPA / Hibernate abstract too much, JDBC too little. It shows, how a modern domain-specific language can greatly increase developer productivity, internalising SQL into Java