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Literals in JPQL and Criteria Queries

Literals in JPQL, as in Java, represent constant values. JPQL supports various types of literals ... . 'abc'), enum literals (e.g. mypackage.MyEnum.MY_VALUE) and entity type literals (e.g. Country). JPQL ... values. Literals should only be embedded in JPQL queries when a single constant value is always used

JPA Query Structure (JPQL / Criteria)

The syntax of the Java Persistence Query Language (JPQL) is very similar to the syntax of SQL ... language and many developers are already familiar with it. The main difference between SQL and JPQL is that SQL works with relational database tables, records and fields, whereas JPQL works with Java

FROM clause (JPQL / Criteria API)

are always polymorphic. JPQL does not provide a way to exclude descendant classes from iteration ... of an entity class in a JPQL query is the unqualified name of the class (e.g. just Country with no package ... variables represent iteration over all the database objects of a specified entity type. JPQL provides

WHERE clause (JPQL / Criteria API)

JPQL query that retrieves selective objects from the database. Out of the four optional clauses of JPQL queries, the WHERE clause is definitely the most frequently used. How a WHERE Clause Works ... for iteration might be very large even if the database is small, making indexes even more essential. JPQL

SELECT clause (JPQL / Criteria API)

The ability to retrieve managed entity objects is a major advantage of JPQL. For example ... 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

Chapter 4 - JPA Queries (JPQL / Criteria)

The JPA Query Language (JPQL) can be considered as an object oriented version of SQL. Users familiar with SQL should find JPQL very easy to learn and use. This chapter explains how to use JPQL as ... , based on JPQL. The first section describes the API that JPA provides for using dynamic and static

Comparison in JPQL and Criteria API

Most JPQL queries use at least one comparison operator in their WHERE clause. Comparison Operators ObjectDB supports two sets of comparison operators, as shown in the following table: Set 1 - JPQL ... . JPQL follows the SQL notation, where Java uses its own notation (which is also in use by JDOQL

JPA Query Expressions (JPQL / Criteria)

Query expressions are the foundations on which JPQL and criteria queries are built. Every query ... 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

Logical Operators in JPQL and Criteria API

Logical operators in JPQL and in JPA criteria queries enable composition of complex JPQL boolean expressions out of simple JPQL boolean expressions. Logical Operators ObjectDB supports 2 sets of logical operators, as shown in the following table: Set 1 - JPQL / SQL Set 2 - Java / JDO AND && OR

ORDER BY clause (JPQL / Criteria API)

The ORDER BY clause specifies a required order for the query results. Any JPQL query that does not ... JPQL expression whose type is comparable (i.e. numbers, strings and date values) and is derived ... are more restrictive. Path expressions are supported by all the JPA implementations but support for other JPQL

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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