java CriteriaBuilder 用自定义条件连接两个表
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CriteriaBuilder join two tables with a custom condition
提问by gvdm
I want to write this SQL query
我想写这个 SQL 查询
SELECT *
FROM A
LEFT OUTER JOIN B
ON A.IDRESOURCE=B.IDRESOURCE AND B.IDLANGUAGE=22;
with the JPA Criteria Builder. I wrote the first part of the join simply with:
使用 JPA 标准生成器。我简单地写了连接的第一部分：
CriteriaQuery<A> searchQuery = criteriaBuilder.createQuery(A.class);
Root<A> aRoot = searchQuery.from(A.class);
Join<A, B> bJoin= aRoot.join("mappedB", JoinType.LEFT);
but I don't know how to implement the condition B.IDLANGUAGE=22.
但我不知道如何实现条件 B.IDLANGUAGE=22。
Is there any way to accomplish this in Criteria Builder?
有什么方法可以在 Criteria Builder 中完成此操作吗？
回答by Neil Stockton
Use JPA 2.1 ONto specify it in the JOINpart, which is notthe same as in the WHERE
使用JPA 2.1ON在指定它JOIN的一部分，这是不一样的WHERE
CriteriaQuery<A> searchQuery = criteriaBuilder.createQuery(A.class);
Root<A> aRoot = searchQuery.from(A.class);
Join<A, B> bJoin= aRoot.join("mappedB", JoinType.LEFT);
bJoin.on(criteriaBuilder.equal(bJoin.get("idLanguage"), 22));
回答by K.Nicholas
Use whereand CriteriaBuilder.equal.
使用where和CriteriaBuilder.equal。
em.select(aRoot).where( criteriaBuilder.equal(bJoin.get("IdLanguage"), 22));
