如何根据存储过程中的条件用另一个变量替换一个变量？

Question

我的帽子下面的存储过程工作正常。不管是谁，我都希望能够检查是否存在具有 YesterdayDate 的数据集，如果不存在，则将 YesterdayDate 替换为 TodayDate.

如果此计数 select count(1) from TableName where DATASET_DATE = YesterdayDate 为 0，我正在尝试类似 cheking 之类的方法，但我找不到一种方法（假设有任何方法）将此检查添加到代码中而不必修改或破坏其他所有内容。

存储过程：

CREATE OR REPLACE function DO_STUFF
(TodayDate date, YesterdayDate date)

return integer is status integer;

BEGIN 

DECLARE
  CURSOR c_stuff
  IS
    SELECT 
        <several_fields>
    FROM 
        TableName TODAY 
        LEFT JOIN TableName YESTERDAY
        ON  TODAY.KEY1 = YESTERDAY.KEY1
        WHERE TODAY.DATASET_DATE = TodayDate
        AND YESTERDAY.DATASET_DATE = YesterdayDate
    ORDER BY 
        TODAY.KEY1 ASC;
BEGIN
  FOR r_lines IN c_stuff
  LOOP
    <do_some_stuff>
  END LOOP;
END;

COMMIT;

STATUS := 0;

return status;

END
/

有人知道如何实现吗？

-- 编辑澄清：我确实需要同时使用这两个谓词。在部分，我主要进行计算和比较两个数据集（今天与昨天）并使用结果更新一些字段。我想在这里完成的是处理昨天过程不是运行并且没有昨天数据集的情况，通过今天与今天的比较并避免结果中的错误数据。

Answer 1

我不确定你想用这个函数做什么。无论我从您的第一行问题中了解到什么，您都可以尝试以下代码 -

CREATE OR REPLACE function DO_STUFF(TodayDate     date,
                                    YesterdayDate date)
RETURN INTEGER
IS
new_date DATE;
CNT NUMBER;
BEGIN
     SELECT COUNT(*)
       INTO CNT
       FROM TableName TODAY 
       LEFT JOIN TableName YESTERDAY ON TODAY.KEY1 = YESTERDAY.KEY1
      WHERE TODAY.DATASET_DATE = TodayDate
        AND YESTERDAY.DATASET_DATE = YesterdayDate
      ORDER BY TODAY.KEY1 ASC;
     IF CNT = 0 THEN
        RETURN TodayDate;
     ELSE
        RETURN YesterdayDate;
     END IF;
EXCEPTION
         WHEN OTHERS THEN
              RETURN '1900-01-01';
END;

Answer 2

不用 JOIN 也能搞定：

CREATE OR REPLACE function DO_STUFF(
  TodayDate date,
  YesterdayDate date
) return integer
IS
  CURSOR c_stuff IS
    SELECT key1,
           field1,
           field2,
           field3
    FROM   (
      SELECT key1,
             field1,
             field2,
             field3,
             DENSE_RANK() OVER (
               ORDER BY CASE dataset_date WHEN YesterdayDate THEN 1 ELSE 2 END
             ) AS rnk
      FROM   TableName 
      WHERE  DATASET_DATE IN ( TodayDate, YesterdayDate )
    )
    WHERE rnk = 1
    ORDER BY KEY1 ASC;
BEGIN 
  FOR r_lines IN c_stuff
  LOOP
    <do_some_stuff>
  END LOOP;

  return 0;
END
/

如何根据存储过程中的条件用另一个变量替换一个变量？

How to replace a variable with another based on a condition in a stored procedure?

sql

oracle

variables

stored-procedures