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Manual
133

Collections in JPQL and Criteria Queries

Collections may appear in JPQL queries: as parameters - when collections are assigned as arguments. as path expressions - in navigation to persistent collection fields. IS [NOT] EMPTY The IS [NOT ... of elements in a specified collection. For example: SIZE(c.languages) is evaluated to the number
Manual
85

Query Parameters in JPA

. Named parameters can be easily identified in a query string by their special form, which is a colon ... are defined implicitly by appearing in the query string. The parameter type is inferred by the context. In ... more occurrences in the query string. A query can be run only after setting values
Manual
84

Literals in JPQL and Criteria Queries

Literals in JPQL, as in Java, represent constant values. JPQL supports various types of literals ... values. Literals should only be embedded in JPQL queries when a single constant value is always used and never replaced. The NULL literal The NULL literal represents a null value, similarly to null in
Manual
83

Locking in JPA

in ObjectDB (and in JPA) is always at the database object level, i.e. each database object is locked ... to pessimistic locking it is easier to use and more efficient. In the rare cases in which update collision ... object. The initial version of a new entity object (when it is stored in the database for the first time
Manual
83

Paths and Types in JPQL and Criteria API

classes) are represented in JPQL by the following types of expressions: Variables - FROM ... persistable classes can participate in direct comparison using the = and <> operators. But more often they are used in JPQL path expressions that navigate to values of simple types (number, boolean
Manual
82

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 ... Equal To >= >= Equal = == Not Equal <> != The two sets differ in the Equal and the Not Equal
Manual
81

Strings in JPQL and Criteria Queries

String values may appear in JPQL queries in various forms: as string literals - e.g. 'abc', ''. as parameters - when string values are assigned as arguments. as path expressions - in navigation ... '%\%' ESCAPE '\' is evaluated to FALSE. In the expressions above only the first percent character
Manual
79

Logical Operators in JPQL and Criteria API

Logical operators in JPQL and in JPA criteria queries enable composition of complex JPQL boolean ... of logical operators, as shown in the following table: Set 1 - JPQL / SQL Set 2 - Java / JDO AND && OR || NOT ! JPQL follows the SQL notation, while Java uses its own notation (which is also in use by JDOQL
Manual
79

Numbers in JPQL and Criteria Queries

Numeric values may appear in JPQL queries in many forms: as numeric literals - e.g. 123, -12.5. as parameters - when numeric values are assigned as arguments. as path expressions - in navigation ... the % (modulo) and the ~ (bitwise complement) operators that are supported in Java and JDO. JPA follows Java
Manual
78

UPDATE SET Queries in JPA/JPQL

Existing entity objects can be updated, as explained in chapter 2, by: Retrieving the entity ... the content of specified entity objects in the database. Updating entity objects in the database using ... with the database. For example, the EntityManager may not be aware that a cached entity object in