使用@Query注释限制结果集 [英] Limiting resultset using @Query anotations

问题描述

我有一个查询，希望限制结果集的大小.由于JPA不支持"LIMIT"，因此我一直在尝试找出正确的方法.我已经尝试过:

I have a query where I want to limit the size of the resultset. As JPA does not support 'LIMIT', I have been trying to work out the correct approach. I have tried:

@Query("SELECT w FROM WardTransaction w WHERE w.visit = :visit ORDER BY w.admissionDateTime DESC").setMaxResults(1)
public WardTransaction findCurrent(@Param("visit") Visit visit);

这是不正确的.我只是在寻找有关正确语法的指导.

Which is not correct. I am just looking for some guidance as to the correct syntax.

我的存储库代码为:

推荐答案

@Query("SELECT w FROM WardTransaction w WHERE w.visit = :visit ORDER BY w.admissionDateTime DESC")

上面是查询方法的定义，要在您的查询中设置MaxMaxResult，您需要使用如下的Pageable对象.

The above is the query method definition, to setMaxResult in your query you need to use Pageable object as it follows.

    @Query("SELECT w FROM WardTransaction w WHERE w.visit = :visit ORDER BY w.admissionDateTime DESC")
public void List<Entities> findAll(Pageable pageable) 

JPA存储库必须实现

JPA repository must implement SimpleJpaRepository

按如下所示设置Pageable对象>

Set Pageable object as it follows>

    Pageable pageSpecification = PageRequest(int page, int size)

Pageable和SimpleJpaRepository的组合是解决方案.

Combination for Pageable and SimpleJpaRepository is the solution.

此处

如果您使用的是EntityManager和NamedQueries，则有一个方法setMaxResult适用于Query对象，但这是另一回事.

If you are using EntityManager and NamedQueries, there is a method setMaxResult that apply to Query object, but it is a different story.

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