JPA 子查询失败答案

【问题标题】：JPA Subquery failsJPA 子查询失败
【发布时间】：2021-09-06 20:28:07
【问题描述】：

有人知道为什么会失败吗？

@Query("SELECT CASE WHEN COUNT(x) > 0 THEN true ELSE false END FROM City a WHERE x.parking= :parking AND x.section= :section AND x.district IN (SELECT uc FROM DistrictCity uc WHERE uc.zone = :zone AND :user IN uc.users)")
Boolean carsExist(String parking, Section section, String zone, User user);

City (class)

String parking
Section section
DistrictCity district

DistrictCity (class)

String Zone
List<User> users (Many to Many relation)

它没有给出语法问题，但它给了我错误“缺少表达式（ORA-00936）” 问题似乎出在 :user IN uc.users

【问题讨论】：

标签： sql spring-boot jpa spring-data-jpa

【解决方案1】：

我认为最后一点是不正确的。这应该有效：

SELECT uc FROM DistrictCity uc JOIN uc.users u WHERE uc.zone = :zone AND u = :user

所以，整个查询变成：

@Query("SELECT CASE WHEN COUNT(x) > 0 THEN true ELSE false END FROM City a WHERE x.parking= :parking AND x.section= :section AND x.district IN (SELECT uc FROM DistrictCity uc JOIN uc.users u WHERE uc.zone = :zone AND u = :user)")

【讨论】：