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39

SELECT clause (JPQL / Criteria API)

objects. JPA 2 adds the ability to use almost any valid JPQL expression in SELECT clauses ... - JPQL does not support the "SELECT *" expression (which is commonly used in SQL). Projection of Path Expressions JPQL queries can also return results that are not entity objects. For example
38

Date and Time in JPQL and Criteria Queries

Date and time expressions may appear in JPQL queries: as date and time literals - e.g. {d '2011-12 ... expressions - in navigation to persistent date and time fields. as results of predefined JPQL current date and time functions. Current Date and Time JPA defines special JPQL expressions
38

Literals in JPQL and Criteria Queries

The CriteriaBuilder interface provides two factory methods for building literal expressions. Ordinary Literals The main method, literal, takes a Java object and returns a literal expression. For example: // Boolean literals: Expression<Boolean> t = cb.literal(true); Expression<Boolean> f = cb
36

GROUP BY and HAVING clauses

which returns the first letters as result. ObjectDB is very flexible in allowing JPQL expressions anywhere in ... . Only identification variables and path expressions are currently supported in the GROUP BY clause by ... of currencies that are in use by countries in that group. The DISTINCT keyword in a COUNT aggregate expression
34

Comparison in JPQL and Criteria API

and expressions that include an unknown value are evaluated as unknown, i.e. to NULL. IS [NOT] NULL ... which are provided by JPQL (and SQL): c.president IS NULL c.president IS NOT NULL The expressions ... ) expressions: c.president == null c.president != null Comparable Data Types Comparison is supported
31

JPA Criteria API Queries

, the range variable, c, is also used in the SELECT clause as the query result expression ... on how to set criteria query clauses and build criteria expressions. Running this query requires setting ... , including in the context of string based JPQL queries. Criteria Query Expressions JPA query clauses
30

Logical Operators in JPQL and Criteria API

expressions out of simple JPQL boolean expressions. Logical Operators ObjectDB supports 2 sets ... part of its JDO support. Criteria Query Logical Operators Boolean Expressions and Predicates Boolean expressions are represented in criteria queries by Expression<Boolean> and descendant interfaces. For example
26

FROM clause (JPQL / Criteria API)

at the WHERE clause level by using a type expression. For example, in the following query, c iterates ... expressions. Join variables can also be bound to path expressions that are based on other join variables ... expression. For example: SELECT c, p.name FROM Country c JOIN c.capital p In this case, the inner loop
26

WHERE clause (JPQL / Criteria API)

to function as a filter. The boolean expression in the WHERE clause, which is also known as the WHERE predicate, defines which objects to accept. Only Country objects for which the predicate expression ... Expressions in WHERE The above queries demonstrate only a small part of the full capabilities
25

Collections in JPQL and Criteria Queries

. as path expressions - in navigation to persistent collection fields. IS [NOT] EMPTY The IS [NOT ... Expressions JPQL collection operators and functions (which are described above) are available also as JPA criteria query expressions. The CriteriaBuilder interface provides factory methods for building

Getting Started

ObjectDB is very easy to use. Follow the Getting Started Tutorial and the Quick Tour manual chapter and in minutes you may be able to write and run first Java programs against ObjectDB.

Prior knowledge or experience in database programming (SQL, JDBC, ORM, JPA, etc.) is not required, but some background in using the Java language is essential.

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