在Hibernate中创建动态sql;我如何实现1 = 1 [英] In Hibernate while creating dynamic sql; how do i implement 1=1

问题描述

我正在使用hibernate。我需要在下面创建查询。在这种情况下，subContest可能为null，在这种情况下， subContest_id =：cont 不应该是where子句的一部分。在创建动态sql时的传统SQL中;对于这种情况，我曾经做过 subContest_id = subContest_id; 但是如何在下面的情况下实现它。这里如果我试图 query.setParameter（cont，subContest_id）; 它会给出异常，因为cont应该是一个id而不是一个字符串。 p>

I am using hibernate. I need to create query below. It is possible the subContest is null in which case subContest_id=:cont should NOT be part of where clause. In conventional SQL when creating dynamic sql ; for such cases I used to do subContest_id = subContest_id ; BUT how do I achieve it in case below. Here If I try to query.setParameter( "cont", "subContest_id " ); it will give exception as cont is supposed to be an id and not a string.

    Query query = getEntityManager().createQuery( "select * from Upload where moderated=:mod, subContest_id=:cont order by lastModifiedTime desc " );
    query.setParameter( "cont", subContest.getId() );

推荐答案

您可以尝试在hibernate中使用条件查询

you can try using criteria query in hibernate

Criteria criteria = session.createCriteria(Upload.class);

您可以添加您的where子句作为限制

you can add your where clause as restrictions

Criteria criteria = session.createCriteria(Upload.class)
    .add(Restrictions.eq("mode", value));

在您的情况下，您希望在添加限制之前检查为空。

in your case you want to check null before adding restriction

if(subContest_id!=null){
        criteria.add(Expression.le("subContest_id",subContest_id));
    }

并且最后可以使用这个命令完成

and finally order by can be done using this

Criteria criteria = session.createCriteria(Upload.class)
    .addOrder( Order.desc("lastModifiedTime") );

请参考 here ，了解如何使用条件查询的详细信息。

please refer here for details on how to use criteria queries

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