PL/SQL 中的连接表

Question

您好，我想问一下我在运行此代码时遇到错误，我能知道如何解决它吗？我想在输入患者 ID 时知道该患者的医生，谢谢。下面是我的代码

DECLARE
  patientid(3)  := &pt_id;
  dname     doc_name%type;
BEGIN
  SELECT doc_name
    INTO dname
    FROM doctor
    JOIN patient
      ON doctor.doc_id = patient.doc_id
   WHERE pt_id = patientid;

  DBMS_OUTPUT.PUT_LINE('He/She is the patient of Dr.' || dname);
END;

Answer 1

patient(3) 应该是什么？缺少数据类型！

不过，考虑一下这样的事情：

SQL> set serveroutput on
SQL> declare
  2    -- No         : patientid(3):=&pt_id;
  3    -- Better     : patientid varchar2(3) := &pt_id;  -- is it VARCHAR2? or NUMBER? Who knows ...
  4    -- Even better:
  5    l_pt_id   patient.pt_id%type := &par_pt_id;
  6    l_dname   doctor.doc_name%type;
  7  begin
  8    select d.doc_name
  9      into l_dname
 10      from doctor d join patient p on d.doc_id = p.doc_id
 11     where p.pt_id = l_pt_id;
 12
 13    dbms_output.put_line ('He/She is the patient of Dr. '|| l_dname);
 14  end;
 15  /
Enter value for par_pt_id: 100
He/She is the patient of Dr. Luffy

PL/SQL procedure successfully completed.

SQL>