80 | JPA Query Expressions (JPQL / Criteria) of JPQL / Criteria query expressions. Atomic Expressions The atomic query expressions are: JPQL / Criteria Variables JPQL / Criteria Parameters JPQL / Criteria Literals Every query expression consists ... Query expressions are the foundations on which JPQL and criteria queries are built. Every query |
53 | Paths and Types in JPQL and Criteria API the query by adding a variable to the FROM clause (representing iteration during query execution). The constructed variable expression can also be used explicitly in other query clauses. Navigation ... classes) are represented in JPQL by the following types of expressions: Variables - FROM |
42 | WHERE clause (JPQL / Criteria API) indexes are defined. WHERE Filter in Multi Variable Queries In a multi-variable query the FROM clause ... the WHERE clause are passed through to the SELECT. In multi-variable queries the number of tuples ... JPQL query that retrieves selective objects from the database. Out of the four optional clauses |
41 | Setting and Tuning of JPA QueriesThe Query and TypedQuery interfaces define various setting and tuning methods that may affect query execution if invoked before a query is run using getResultList or getSingleResult. Result Range ... window that exposes a portion of a large query result list (hiding anything outside that window |
40 | Query Parameters in JPAQuery parameters enable the definition of reusable queries. Such queries can be executed with different parameter values to retrieve different results. Running the same query multiple times with different parameter values (arguments) is more efficient than using a new query string for every query |
39 | Running JPA QueriesThe Query interface defines two methods for running SELECT queries: Query.getSingleResult - for use when exactly one result object is expected. Query.getResultList - for general use in any other case ... other case. In addition, the Query interface defines a method for running DELETE and UPDATE queries |
39 | JPA Named QueriesA named query is a statically defined query with a predefined unchangeable query string. Using named queries instead of dynamic queries may improve code organization by separating the JPQL query strings from the Java code. It also enforces the use of query parameters rather than embedding literals |
38 | JPA Query APIQueries are represented in JPA 2 by two interfaces - the old Query interface, which was the only interface available for representing queries in JPA 1, and the new TypedQuery interface that was introduced in JPA 2. The TypedQuery interface extends the Query interface. In JPA 2 the Query interface |
37 | SELECT clause (JPQL / Criteria API), the following query returns Country objects that become managed by the EntityManager em: TypedQuery<Country> query = em.createQuery("SELECT c FROM Country c", Country.class); List<Country> results = query.getResultList(); Because the results are managed entity objects they have all the support |
4 | javax.jdo.Query variableDeclaration - the name of the variable in the outer query to bind the results of the subquery ... . Parameters: sub - the subquery to add to this Query variableDeclaration - the name of the variable ... - the name of the variable to be used in this Query candidateCollectionExpression - the candidate |
