带有 CriteriaQuery 的 where 子句中的子查询

Subquery in where clause with CriteriaQuery(带有 CriteriaQuery 的 where 子句中的子查询)

问题描述

谁能给我一些关于如何将这种子查询放入 CriteriaQuery 的提示?(我正在使用 JPA 2.0 - Hibernate 4.x)

Can anybody give me some hints on how to put that kind of subquery in a CriteriaQuery? (I'm using JPA 2.0 - Hibernate 4.x)

SELECT a, b, c FROM tableA WHERE a = (SELECT d FROM tableB WHERE tableB.id = 3) - 第二次选择将始终得到单个结果或 null.

SELECT a, b, c FROM tableA WHERE a = (SELECT d FROM tableB WHERE tableB.id = 3) - the second select will always get a single result or null.

推荐答案

试试下面的例子来创建一个子查询:

Try something like the following example to create a subquery:

CriteriaQuery<Object[]> cq = cb.createQuery(Object[].class);
Root tableA = cq.from(TableA.class);

Subquery<String> sq = cq.subquery(TableB.class);
Root tableB = cq.from(TableB.class);
sq.select(tableB.get("d"));
sq.where(cb.equal(tableB.get("id"), 3));

cq.multiselect(
    cb.get("a"),
    cb.get("b"),
    cb.get("c"));
cq.where(cb.equal(tableA.get("a"), sq));
List<Object[]> = em.createQuery(cq).getResultList();

请注意，由于附近缺少 IDE，代码尚未经过测试.

Note the code has not been tested due to the lack of an IDE nearby.

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