关系代数帮助

Question

我是关系代数的新手，发现它很困难。我已经回答了几个问题；然而，它们相对简单。不过，可以在这些方面提供帮助。

数据库

Patient (PatientCode, PatientSurname, PatientFirstname, PatientSex, PatientAge,
         PatientOccupation, PatientHeight, PatientWeight, PatientAddress) 

Doctor (DoctorCode, DoctorSurName,  DoctorFirstName, DoctorPrivateAddress,
        MobileNo, Doctor Specialisim) 

Operation (Operation Code, PatientCode, DoctorCode, Date, Time, Result,
           OperationType) 

Is_Seen_By (PatientCode, DoctorCode, Date, Time)

查询

1. 查找被医生“DR333”做过手术的患者的姓氏和性别，结果没有成功。

2. 查找 2010 年 11 月 18 日已完成且成功的操作的代码。另请列出参与手术的医生姓名。

Answer 1

这可能是完全错误的，也可能不是完全错误的，我刚刚结束了很长的计算机休假。它的 SQL 应该类似于：

Q1:

SELECT Patient.PatientSurname, Patient.PatientSex
  FROM Patient INNER JOIN Operation
    ON Operation.PatientCode = Patient.PatientCode
 INNER JOIN DOCTOR ON Operation.DoctorCode = Doctor.DoctorCode
 WHERE Operation.Result = "fail"
   AND Doctor.DoctorCode = "DR333"

Q2:

SELECT Operation.OperationCode, Doctor.DoctorFirstName
  FROM Operation INNER JOIN Doctor ON Operation.DoctorCode = Doctor.DoctorCode
 WHERE Operation.Date = "18/11/2010"
   AND Operation.Result = "success"