我是新來的關係代數和我的任務,我必須創建兩個。我已經寫出了SQL中遇到的問題,但我不確定如何在關係代數中表示這種聯接。任何幫助/指針將不勝感激。我如何表示我在關係代數中的加入?
SELECT ps.FirstName AS StudentFirstName, ps.LastName AS StudentLastName, pst.FirstName AS StaffFirstName , pst.LastName AS StaffLastName, pg.FirstName AS GuardianFirstName, pg.LastName AS GuadianLastName, i.DateTimeReported, i.NatureOfIllness
FROM Incident i
JOIN Student s USING (StudentID)
JOIN Person ps ON (s.StudentID = ps.PersonID)
JOIN Staff st USING (StaffID)
JOIN Person pst ON (st.StaffID = pst.PersonID)
JOIN Guardian g USING (GuardianID)
JOIN Person pg ON (g.GuardianID = pg.PersonID)
WHERE i.DecisionMade IS NULL;
我有一種感覺,你的數據庫設計是非常尷尬的與 – 2009-01-13 00:46:38