SELECT clause

For finder and select queries, the syntax of the SELECT clause is as follows:

SELECT  [  ALL | DISTINCT  ]  
	{ single-valued-path-expression  |  OBJECT ( identification-variable )  }

The SELECT clause consists of either a single identification variable that is defined in the FROM clause or a single valued path expression that evaluates to a object reference or CMP value. The keyword DISTINCT can be used to eliminate duplicate references.

For a query that defines a finder method the query must return an object type consistent with the home for which the finder method associated with the query. In other words, a finder method for a department home can not return employee objects.

A scalar-subselect is a subselect that returns a single value.

Example: SELECT clause

Find all employees that earn more than John:

SELECT OBJECT(e) FROM EmpBean ej, EmpBean e 
WHERE  ej.name = 'John'  and e.salary > ej.salary

Find all departments that have one or more employees who earn less than 20000:

SELECT DISTINCT  e.dept  FROM EmpBean e where e.salary < 20000

A select method query can have a path expression that evaluates to an arbitrary value:

SELECT  e.dept.name  FROM EmpBean e where e.salary < 2000

The above query returns a collection of name values for those departments having employees earning less than 20000.

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EJB query language

Using EJB query
    

 

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