[jboss-user][JPQL EJBQL JBossQL] Problem with using "Limit" at JPQL subquery

JBoss-4.2.3.GA / Eclipse 3.4 with JBoss Tools 2.12.GA / PostgresQL 8.1 / JDK 1.6 I want using Limit in my JPQL subquery : "select questions " + "from Question questions " + "where questions in ( SELECT questions " + "FROM questions " + "WHERE questions.typeBean.typeId IN ( :typeId ) " + "AND questions.questionTypeBean.questionTypeId IN ( :questionTypeId ) " + "ORDER BY random() Limit ( :limit ) ) " + "ORDER BY questions.questionFlag " "random()" can be used, but "Limit" is useless, and I found org.jboss.ejb.plugins.cmp.ejbql.ASTLimitOffset at jboss.jar, how could I using "Limit" ? And, is "random()" is supported by jboss or other one ? Best regards, Zhang ZeHao