Subqueries

A subquery can be used in quantified predicates, the EXISTS predicate, or the IN predicate. A subquery should only specify a single element in the SELECT clause.

When a path expression appears in a subquery, the identification variable of the path expression must be defined either in the subquery, in one of the containing subqueries, or in the outer query. A scalar subquery is a subquery that returns one value. A scalar subquery can be used in a basic predicate and in the SELECT clause of a dynamic query.

Example: Subqueries

SELECT OBJECT(e) FROM EmpBean e WHERE e.salary > ( SELECT AVG(e1.salary) FROM EmpBean e1)

The previous query returns employees who earn more than average salary of all employees.

SELECT OBJECT(e) FROM EmpBean e WHERE e.salary > ( SELECT AVG(e1.salary) FROM IN (e.dept.emps) e1 )

The previous query returns employees who earn more than average salary of their department.

SELECT OBJECT(e) FROM EmpBean e WHERE e.salary = ( SELECT MAX(e1.salary) FROM IN (e.dept.emps) e1 )

The previous query returns employees who earn the most in their department.

 SELECT OBJECT(e) FROM EmpBean e
WHERE e.salary > ( SELECT AVG(e.salary) FROM EmpBean e1  WHERE YEAR(e1.hireDate) =  YEAR(e.hireDate)  )

The previous query returns employees who earn more than the average of employees hired in same year.

Related concepts

EJB query language

Related tasks

Use EJB query