从日期属性中提取日期

Question

所以我有这张桌子--

create table orders (
ono      number(5) not null primary key,
cno      number(5) references customers,
eno      number(4) references employees,
received date,
shipped  date);

使用下面的脚本填充--

insert into orders values
(1020,1111,1000,'10-DEC-11','12-DEC-11');
insert into orders values
(1021,1111,1000,'12-JAN-12','15-JAN-12');
insert into orders values
(1022,2222,1001,'13-FEB-12','20-FEB-12');
insert into orders values
(1023,3333,1000,'12-MAR-12',null);

现在我正在尝试创建一个PL/SQL Procedure，它将输入作为一个月并显示该特定月份的订单。看来我只是无法正确获得EXTRACT()。这是我的代码块

CREATE OR REPLACE PROCEDURE TEST_REPORT
    (MONTH_NUMBER IN NUMBER )

    AS
     V_MONTH VARCHAR2(10);
    BEGIN

    SELECT RECEIVED INTO V_MONTH
    FROM ORDERS WHERE EXTRACT(MONTH FROM TO_DATE(
    ORDERS.RECEIVED, 'DD-MON-RR'))=MONTH_NUMBER;
    END TEST_REPORT;

我在这里做错了什么？作为记录，它编译并执行但不显示任何内容。

非常感谢

尝试 2

CREATE OR REPLACE PROCEDURE TEST_REPORT
    (MONTH_NUMBER IN NUMBER )

DECLARE
   CURSOR C1 IS SELECT RECEIVED INTO V_MONTH
   FROM ORDERS
   WHERE EXTRACT(MONTH FROM ORDERS.RECEIVED) = MONTH_NUMBER;
   V_DATE ORDERS.RECEIVED%TYPE;
BEGIN

     OPEN C1;
  LOOP
    FETCH C1 INTO V_DATE;
    IF C1%FOUND THEN  -- fetch succeeded
      DBMS_OUTPUT.PUT_LINE('DATE ' || V_DATE);
    ELSE  -- fetch failed, so exit loop
      EXIT;
    END IF;
  END LOOP;
END TEST_REPORT;

Answer 1

只是以另一种方式处理多条记录，我们可以使用 不建议将 BULK COLLECT 作为逐行处理，如果 数据量巨大。海量数据——更多的上下文切换。让我知道 如果这有帮助。

CREATE OR REPLACE PROCEDURE TEST_REPORT(
    MONTH_NUMBER IN NUMBER )
AS
TYPE v_rcvd
IS
  TABLE OF ORDERS.RECEIVED%TYPE;
  v_rcvd_tab v_rcvd;
BEGIN
  SELECT RECEIVED BULK COLLECT
  INTO v_rcvd_tab
  FROM ORDERS
  WHERE EXTRACT(MONTH FROM ORDERS.RECEIVED) = MONTH_NUMBER;
  IF v_rcvd_tab.EXISTS(1) THEN
    FOR I IN v_rcvd_tab.FIRST..v_rcvd_tab.LAST
    LOOP
      DBMS_OUTPUT.PUT_LINE('DATE ' || v_rcvd_tab(i));
    END LOOP;
  END IF;
END TEST_REPORT;

Answer 2

由于 'received' 的类型是 DATE，因此您不应在其上使用 TO_DATE。 TO_DATE 用于将字符串 (VARCHAR2) 解析为日期格式。准确地说，它不应该给你带来麻烦，但我已经遇到了奇怪的行为。

替换以下查询：

SELECT RECEIVED INTO V_MONTH
  FROM ORDERS
 WHERE EXTRACT(MONTH FROM TO_DATE(ORDERS.RECEIVED, 'DD-MON-RR'))=MONTH_NUMBER;

有了这个：

SELECT RECEIVED INTO V_MONTH
  FROM ORDERS
 WHERE EXTRACT(MONTH FROM ORDERS.RECEIVED) = MONTH_NUMBER;
 DBMS_OUTPUT.PUT_LINE(V_MONTH); --Print your result.

更多信息和 EXTRACT 示例可以在documentation 中找到。

此外，您应该注意，如果有多个行适合您的查询，则会引发异常，因为 v_month 的类型为 VARCHAR2。您应该考虑使用集合或迭代游标。可以在here 找到一个完全符合您需求的隐式游标的简单示例。

编辑：在我们的谈话之后，这是您的情况的解决方案：

CREATE OR REPLACE PROCEDURE TEST_REPORT 
(MONTH_NUMBER IN NUMBER ) 

AS 
    CURSOR C1 IS SELECT RECEIVED 
                   FROM ORDERS 
                  WHERE EXTRACT(MONTH FROM ORDERS.RECEIVED) = MONTH_NUMBER; 
    V_DATE ORDERS.RECEIVED%TYPE; 
BEGIN 

    OPEN C1; 
    LOOP 
        FETCH C1 INTO V_DATE; 
        IF C1%FOUND THEN -- fetch succeeded 
            DBMS_OUTPUT.PUT_LINE('DATE ' || V_DATE); 
        ELSE -- fetch failed, so exit loop 
            EXIT; 
        END IF; 
    END LOOP; 
END TEST_REPORT;