PLSQL程序通過結果

Question

我有兩個表

圖書查詢兩個表和循環一本書（Book.no_of_copies是5，然後在副本表中有5個副本（行））

我該怎麼寫一個可以將輸入參數作爲book_id的過程，並且首先查詢Book表，找到no_of_copies。如果no_of_copies是肯定的，則查詢Copies表並顯示每個結果的copy_number，shelf_letter和call_number。

Answer 1

CREATE PROCEDURE (P_BOOK_ID INTEGER) 

    CURSOR C1(L_BOOK_ID INTEGER) IS 
    SELECT * FROM COPIES WHERE BOOK_ID = L_BOOK_ID; 
    L_NUM_COPIES NUMBER; 

BEGIN 

    SELECT NO_OF_COPIES INTO L_NUM_COPIES FROM BOOK WHERE BOOK_ID = P_BOOK_ID; 

    IF L_NUM_COPIES>0 
     THEN 
      FOR CUR IN C1(P_BOOK_ID) 
      LOOP 
       DBMS_OUTPUT.PUT_LINE(CUR.COPY_NUMBER); 
      END LOOP; 

END; 

OR

CREATE PROCEDURE (P_BOOK_ID INTEGER) 

    CURSOR C1(L_BOOK_ID INTEGER) IS 
    SELECT B.book_id, 
      B.shelf_letter, 
      B.call_number, 
      B.no_of_copies, 
      C.copy_id, 
      C.copy_number 
    FROM COPIES C, 
     BOOK B 
    WHERE C.BOOK_ID = L_BOOK_ID 
    AND C.BOOK_ID=B.BOOK_ID; 

    L_NUM_COPIES NUMBER; 

BEGIN 

    FOR CUR IN C1(P_BOOK_ID) 
    LOOP 
     DBMS_OUTPUT.PUT_LINE(CUR.book_id); 
     DBMS_OUTPUT.PUT_LINE(CUR.shelf_letter); 
     DBMS_OUTPUT.PUT_LINE(CUR.call_number); 
     DBMS_OUTPUT.PUT_LINE(CUR.no_of_copies); 
     DBMS_OUTPUT.PUT_LINE(CUR.copy_id); 
     DBMS_OUTPUT.PUT_LINE(CUR.copy_number); 

    END LOOP; 

END; 

Answer 2

...或者，呃，你可以只寫這個非常簡單的查詢：

select copies.copy_number, 
     book.shelf_letter, 
     book.call_number 
from book 
join copies 
on  copies.book_id = book.book_id 
where book.book_id  = ??? 
and book.no_of_copies > 0 

如果非要你可以用這一個過程，但我無法想象你爲什麼需要。