将SQL写入关系代数

Question

如何将此SQL查询写入关系代数？

Select Distinct S.Name
From Student S, Transcript T1, Transcript T2
WHERE T1.StudId = S.Id AND T2.StudId = S.Id And
(T1.Semester =’S1997’ AND T2.Semester = ’F1998’)

Answer 1

当我无法测试它并且我不知道你的关系模式时，说出确切的表达有点难，但是试试这样的smth

\project_{Name}
{
    {
        Student \join_{Id = StudId} \select_{Semester='S1997'} Transcript
    } \join_{Id = StudId}
    {
       \select_{Semester='F1998'} Transcript
    }
}