hibernate关联查询纯SQL的实现(mysql)

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两张表关联查询,学生表和学生学习记录表,学生表是学生的基本信息,学习记录主要是每天背诵的单词记录,包括单词对错

的个数

ifnull:如果是空则为...

left join左连接,左表全部显示,右表没有匹配字段显示空

left join后面一张表的查询结果,用到哪个字段查询哪个字段,没必要全部查询

//班级里的学生单词背诵查询

public List<RecitingStudent> findTotalStudents(int classId, Timestamp start, Timestamp end) {
    Session session = getSessionFactory().getCurrentSession();
    String query = "SELECT s.studentId, s.name, ifnull(sum(m.correct_number),0) as correct, ifnull(sum(m.error_number),0) as error from " +
            "student s " +
            "LEFT JOIN " +
            "(SELECT studentId,correct_number,error_number FROM " +
            "reciting_notes r " +
            "WHERE r.uploadTime BETWEEN ? AND ?) m " +
            "ON " +
            "s.studentId = m.studentId " +
            "where " +
            "s.classId=? " +
            "GROUP BY s.studentId";
    Query query1 = session.createSQLQuery(query).addScalar("studentId",StandardBasicTypes.INTEGER).
            addScalar("name",StandardBasicTypes.STRING).
            addScalar("correct", StandardBasicTypes.INTEGER).
            addScalar("error",StandardBasicTypes.INTEGER);
    query1.setParameter(0, start);
    query1.setParameter(1, end);
    query1.setParameter(2, classId);
    List list = query1.list();
    List<RecitingStudent> recitingStudents = new ArrayList<>();
    for(Iterator iterator = list.iterator(); iterator.hasNext();){
        //每个集合元素都是一个数组，数组元素列值
        Object[] objects = (Object[]) iterator.next();
        RecitingStudent recitingStudent = new RecitingStudent();
        recitingStudent.setStudentId((Integer) objects[0]);
        recitingStudent.setName((String) objects[1]);
        recitingStudent.setCorrect((Integer) objects[2]);
        recitingStudent.setError((Integer) objects[3]);
        recitingStudents.add(recitingStudent);
    }
    return recitingStudents;
}

}