In this chapter we have taken a complete tour of the Java Persistence Query Language, looking at the numerous query types and the syntax for each. We covered the history of the language, from its roots in the EJB 2.0 specification to the major enhancements introduced by the Java Persistence API.
In the section on select queries, we explored each query clause and incrementally built up more complex queries as the full syntax was described. We discussed identification variables and path expressions, which are used to navigate through the domain model in query expressions. We also looked at the various conditional expressions supported by the language.
In our discussion of aggregate queries we introduced the additional grouping and filtering clauses that extend select queries. We also demonstrated the various aggregate functions.
In the sections on update and delete queries, we described the full syntax for bulk update and delete statements, the runtime behavior of which was described in the previous chapter.
In the next chapter we switch back to object-relational mapping and cover advanced concepts such as inheritance, composite primary keys and associations, and multiple table mappings.
KeywordsIdentification Variable Conditional Expression Aggregate Function Query Engine Path Expression
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