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我正在研究一个包含一些程序的包，但遇到了一些麻烦。当我尝试测试将加仑转换为升的过程或其他过程时，它只是打印出在未命名块中声明的内容，而不是转换数字。有任何想法吗？

CREATE OR REPLACE PACKAGE eng_metric 
IS 
  PROCEDURE convert(degree_fahrenheit  IN OUT NUMBER,degree_celsius  IN OUT NUMBER,measure  IN VARCHAR2); 

  PROCEDURE convert(liters  IN OUT NUMBER,gallons  IN OUT NUMBER); 
END eng_metric; 
/ 

CREATE OR REPLACE PACKAGE BODY eng_metric 
AS 
  PROCEDURE Convert 
       (degree_fahrenheit  IN OUT NUMBER, 
        degree_celsius     IN OUT NUMBER, 
        measure            IN VARCHAR2) 
  IS 
    df         NUMBER; 
    dc         NUMBER; 
    convertf   NUMBER; 
    measurecf  VARCHAR2(4); 
  BEGIN 
    measurecf := measure; 

    df := degree_fahrenheit; 

    dc := degree_celsius; 

    IF measure = 'TEMP' THEN 
      IF dc = NULL THEN 
        convertf := ((df - 32) * .56); 

        degree_fahrenheit := convertf; 

        dbms_output.Put_line('The temperature in fahrenheit is ' 
                             ||To_char(degree_fahrenheit)); 
      ELSIF df = NULL THEN 
        convertf := (dc + 17.98) * 1.8; 

        degree_celsius := convertf; 
      END IF; 
    ELSE 
      dbms_output.Put_line('Invalid measure'); 
    END IF; 
  END convert; 

  PROCEDURE Convert 
       (liters   IN OUT NUMBER, 
        gallons  IN OUT NUMBER) 
  IS 
    lit        NUMBER; 
    gal        NUMBER; 
    convertlg  NUMBER; 
  BEGIN 
    lit := liters; 

    gal := gallons; 

    IF gal = NULL THEN 
      convertlg := (lit / 3.785); 

      liters := convertlg; 
    ELSIF lit = NULL THEN 
      convertlg := (gal * 3.785); 

      gallons := convertlg; 
    END IF; 
  END convert; 
END eng_metric; 
/ 

DECLARE 
  liters   NUMBER := 25; 
   gallons  NUMBER := 41; 
   nully    NUMBER := NULL; 
BEGIN 
  eng_metric.Convert(nully,gallons); 

  dbms_output.Put_line(To_char(gallons)); 
END; 
/
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2 回答 2

4

代替

IF gal = NULL THEN

你需要

IF gal IS NULL
于 2009-04-16T00:40:32.713 回答
0

您必须记住的是，NULL 表示“没有价值”。它从不等于或不等于任何东西，包括 NULL。所以你需要使用 IS NULL 或 IS NOT NULL，或者使用 NVL 函数将 null 更改为有值的东西。

于 2009-04-16T23:58:16.020 回答