JDOQL子查询计数问题

Question

我在使用JDOQL进行子查询计数时遇到问题（使用DataNucleus）。以下查询

SELECT this.price
FROM com.mysema.query.jdo.test.domain.Product
WHERE (SELECT count(other)
FROM com.mysema.query.jdo.test.domain.Product other
WHERE other.price > this.price) > a1
PARAMETERS java.lang.Long a1

导致异常

javax.jdo.JDOUserException: Cannot perform operation ">" on SubqueryExpression "(SELECT COUNT("OTHER".PRODUCT_ID) FROM PRODUCT "OTHER" WHERE "OTHER".PRICE > THIS.PRICE)" and IntegerLiteral "?"
    at org.datanucleus.jdo.NucleusJDOHelper.getJDOExceptionForNucleusException(NucleusJDOHelper.java:390)
    at org.datanucleus.jdo.JDOQuery.executeWithArray(JDOQuery.java:321)

以下查询既不起作用：

SELECT this.price
FROM com.mysema.query.jdo.test.domain.Product
WHERE !(SELECT other
FROM com.mysema.query.jdo.test.domain.Product other
WHERE other.price > this.price).isEmpty()

确保子查询结果不为空的正确方法是什么？

Answer 1

我通过从DataNucleus 2.0.4升级到2.1.2来解决问题。第一个查询有效。