java - 动态属性名称搜索

Question

假设我有一个像这样的学生表:

student_id   name   address ...   school   employer
    1      Chris    2 John         UofJ     J Limited
    2      Ann      3 Doe          UofD     D limited

现在我需要查找拥有学校 = 'UofJ' 和雇主 = 'J Limited' 的学生列表。简单:

select * from student where school = 'UofJ' and employer = 'J Limited'

但是，我的现实是最后 2 个属性作为列存储在学生表中，但作为行存储在名为 student_attribute 的单独表中:

student_attribute_id    student_id    attribute_name    attribute_value
       1                    1            school            UofJ
       1                    1            company           J Limited
       1                    2            school            UofD
       1                    2            company           D Limited

我的任务是从这个 student_attribute 表中查找学生 ID 列表，该表仍然基于 school = 'UofJ' 和 employer = 'J Limited'。我该怎么做？

而且，我使用Springboot JPS存储库来进行查询，所以我愿意听取sql方式或JPA方式的解决方案。

Answer 1

您可以使用条件聚合来找出哪个student_id同时满足两个条件。

select student_id
from student_attribute
group by student_id
having count(case 
            when attribute_name = 'school'
                and attribute_value = 'UofJ'
                then 1
            end) > 0
    and count(case 
            when attribute_name = 'company'
                and attribute_value = 'J Limited'
                then 1
            end) > 0

然后您可以将其与学生表连接以获取相应的详细信息。

select s.*
from student s
join (
    select student_id
    from student_attribute
    group by student_id
    having count(case 
                when attribute_name = 'school'
                    and attribute_value = 'UofJ'
                    then 1
                end) > 0
        and count(case 
                when attribute_name = 'company'
                    and attribute_value = 'J Limited'
                    then 1
                end) > 0
    ) a on s.student_id = a.student_id;