对JPQL感到困惑 [英] Confusing about JPQL

问题描述

我想让JPQL喜欢以下示例:

I want to JPQL likes following example:

让酒店"对象具有客户"和组织"两个对象.如果客户不为空，则组织将为空.并且如果Customer为null，则组织不会为null.所以

Let Hotel object has two objects of Customer and Organization. If Customer is not null, organization will be null. And if the Customer is null , organization will not be null. So

我JPQL喜欢这个；

I JPQL likes this;

从酒店h中选择h.customer.name.firstName和h.organization.name

Select h.customer.name.firstName, h.organization.name from Hotel h

我只想将这两个结果之一分配给一个变量，因为一个总是为空. 谢谢你，我的英语很抱歉.

i want to assign one of these two result only to one variable because one is always null. Thanks and Sorry for my english.

推荐答案

可能您正在寻找COALESCE()函数.请尝试以下操作:

Probably, you are looking for COALESCE() function. Try the following:

SELECT COALESCE(h.customer.name.firstName, h.organization.name) FROM Hotel h

如果需要，还可以使用CASE表达式.

You also can use CASE expression if you want.

更多详细信息: http://docs.jboss.org/hibernate/orm/4.2/devguide/zh-CN/html/ch11.html#d5e3257

这篇关于对JPQL感到困惑的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！