EJB query language

 

EJB query langauge enables you to write queries based on entity beans without knowing the underlying relational schema. An EJB query is a string that contains the following elements:

• a SELECT clause that specifies the enterprise beans or values to return;

• a FROM clause that names the bean collections;

• an optional WHERE clause that contains search predicates over the collections;

• an optional GROUP BY and HAVING clause (see Aggregation functions);

• an optional ORDER BY clause that specifies the ordering of the result collection.

Collections of entity beans are identified in EJB queries through the use of their abstract schema name in the query FROM clause.

The elements of EJB query language are discussed in more detail in the following related topics.

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Sub-topics

Example: Queries with EJB

FROM clause

Inheritance in EJB query

Path expressions

WHERE clause

Scalar functions

Aggregation functions

SELECT clause

ORDER BY clause

UNION operation

Subqueries

EJB query language limitations and restrictions

EJB query compatibility issues with SQL

Database restrictions for EJB query

Rules for data type manipulation in EJB query

EJB query: Reserved words

EJB query: BNF syntax

Comparison of EJB 2.1 specification and WebSphere query language

 

Related tasks

Use EJB query