ORA-00913: 嵌套大小写的值过多

Question

我目前正在执行我的第一年任务，即使用 Oracle Apex 构建数据库，并尝试创建一个包含字段以过滤显示的表格的报告。为此，请使用 2 个参数（在本例中为牙医预约日期和执行所述预约的工作人员），我使用嵌套案例来检查每个字段。我收到错误：

ORA-06550：第 6 行，第 23 列：ORA-00913：值太多。

我、我的同学和我的导师都没有找到解决方法。希望这里的人能看到我的错误。

这是我的代码：

SELECT 
CASE :P5_APPOINTMENT_DATE
    WHEN (NULL)
        THEN CASE :P5_STAFF
            WHEN (NULL)
                THEN (select
                      APPOINTMENT_ID AS "Appointment ID",
                      Patient.Surname AS "Patient Surname",
                      Patient.Forename AS "Patient Forename",
                      Staff.Surname AS "Staff Surname",
                      A_DATE AS "Date"
                      FROM Appointment
                      Inner Join Patient ON Patient.Patient_ID = Appointment.Patient_ID
                      Inner Join Staff ON Staff.Staff_ID = Appointment.Staff_ID)

                ELSE (select
                      APPOINTMENT_ID AS "Appointment ID",
                      Patient.Surname AS "Patient Surname",
                      Patient.Forename AS "Patient Forename",
                      Staff.Surname AS "Staff Surname",
                      A_DATE AS "Date"
                      FROM Appointment
                      Inner Join Patient ON Patient.Patient_ID = Appointment.Patient_ID
                      Inner Join Staff ON Staff.Staff_ID = Appointment.Staff_ID
                      Where STAFF.STAFF_ID = :P5_STAFF) 
                END 


        ELSE CASE :P5_STAFF
            WHEN (NULL)
                THEN (select
                      APPOINTMENT_ID AS "Appointment ID",
                      Patient.Surname AS "Patient Surname",
                      Patient.Forename AS "Patient Forename",
                      Staff.Surname AS "Staff Surname",
                      A_DATE AS "Date"
                      FROM Appointment
                      Inner Join Patient ON Patient.Patient_ID = Appointment.Patient_ID
                      Inner Join Staff ON Staff.Staff_ID = Appointment.Staff_ID
                      Where A_DATE = :P5_APPOINTMENT_DATE)
                ELSE (select
                      APPOINTMENT_ID AS "Appointment ID",
                      Patient.Surname AS "Patient Surname",
                      Patient.Forename AS "Patient Forename",
                      Staff.Surname AS "Staff Surname",
                      A_DATE AS "Date"
                      FROM Appointment
                      Inner Join Patient ON Patient.Patient_ID = Appointment.Patient_ID
                      Inner Join Staff ON Staff.Staff_ID = Appointment.Staff_ID
                      Where A_DATE = :P5_APPOINTMENT_DATE AND STAFF.Surname = :P5_STAFF)
                END

        END
        FROM APPOINTMENT

Answer 1

正如 Gordon Linoff 在评论中所说，case 返回单个值。由于大部分子查询是相同的并且您只是改变过滤条件，您可以将case 移动到where 子句；除了这里你甚至不需要一个案例，你可以用or得到同样的效果，比如：

SELECT APPOINTMENT_ID AS "Appointment ID",
  Patient.Surname AS "Patient Surname",
  Patient.Forename AS "Patient Forename",
  Staff.Surname AS "Staff Surname",
  A_Date AS "Date"
FROM Appointment
JOIN Patient ON Patient.Patient_ID = Appointment.Patient_ID
JOIN Staff ON Staff.Staff_ID = Appointment.Staff_ID
WHERE (:P5_APPOINTMENT_DATE IS NULL OR A_Date = :P5_APPOINTMENT_DATE)
AND (:P5_STAFF IS NULL OR STAFF.Surname = :P5_STAFF);

如果两个绑定变量都为空，您将获得所有记录；如果其中一个或两个都不为空，那么您将获得匹配值的子集。这似乎是您想要的 - 四种可能的结果，具体取决于设置了两个变量中的哪一个。