select x from Magazine x

The preceding is a simple EJBQL query for all Magazine entities.

public Query createQuery (String ejbql);

The EntityManager.createQuery method creates a Query instance from a given EJBQL string.

public List getResultList ();

Invoking Query.getResultList executes the query and returns a List containing the matching objects. The following example executes our Magazine query above:

EntityManager em = ...
Query q = em.createQuery ("select x from Magazine x");
List<Magazine> results = q.getResultList ();

An EJBQL query has an internal namespace declared in the from clause of the query. Arbitrary identifiers are assigned to entities so that they can be referenced elsewhere in the query. In the query example above, the identifier x is assigned to the entity Magazine.

	Note
	The as keyword can optionally be used when declaring identifiers in the from clause. select x from Magazine x and select x from Magazine as x are synonymous.

Following the select clause of the query is the object or objects that the query returns. In the case of the query above, the query's result list will contain instances of the Magazine class.

	Note
	When selecting entities, you can optionall use the keyword object. The clauses select x and select object(x) are synonymous.

The optional where clause places criteria on matching results. For example:

select x from Magazine x where x.title = 'JDJ'

Keywords in EJBQL expressions are case-insensitive, but entity, identifier, and member names are not. For example, the expression above could also be expressed as:

SELECT x FROM Magazine x WHERE x.title = 'JDJ'

But it could not be expressed as:

SELECT x FROM Magazine x WHERE x.TITLE = 'JDJ'

As with the select clause, alias names in the where clause are resolved to the entity declared in the from clause. The query above could be described in English as "for all Magazine instances x, return a list of every x such that x's title field is equal to 'JDJ'".

EJBQL uses SQL-like syntax for query criteria. The and and or logical operators chain multiple criteria together:

select x from Magazine x where x.title = 'JDJ' or x.title = 'JavaPro'

The = operator tests for equality. <> tests for inequality. EJBQL also supports the following arithmetic operators for numeric comparisons: >, >=, <, <=. For example:

select x from Magazine x where x.price > 3.00 and x.price <= 5.00

This query returns all magazines whose price is greater than 3.00 and less than or equal to 5.00.

select x from Magazine x where x.price <> 3.00

This query returns all Magazines whose price is not equals to 3.00.

You can group expressions together using parentheses in order to specify how they are evaluated. This is similar to how parentheses are used in Java. For example:

select x from Magazine x where (x.price > 3.00 and x.price <= 5.00) or x.price = 7.00

This expression would match magazines whose price is 4.00, 5.00, or 7.00, but not 6.00. Alternately:

select x from Magazine x where x.price > 3.00 and (x.price <= 5.00 or x.price = 7.00)

This expression will magazines whose price is 5.00 or 7.00, but not 4.00 or 6.00.

EJBQL also includes the following conditionals: