如何去除 Teradata sql 中的變量並在 select 語句中調用它們？

Question

我想聲明兩個變量並在 teradata 中 select 語句的 where 條件下使用 thoes 變量，但我收到了一個錯誤。

Create Procedure Demo()

Begin
Declare REnd Date;
Declare RStart Date;

Set REnd = (select max(CalendarDate) as REnd 
            from Table1 
            where CalendarDate = MonthEndDate
            and  Monthofyear in ('June', 'December')
            and CalendarDate < Current_date()
           );

Set RStart = (select max(CalendarDate) as RStart
            from Table1 
            where CalendarDate = (CalendarDate - Extract(Day From CalendarDate)+1)
            and  Monthofyear in ('January', 'July')
            and CalendarDate < REnd
           );

Call dbc.sysexecsql(('select * from table 2 where reviewdate between' ||REnd|| 'and' ||RStart|| ');');
End;

Answer 1

不需要動態 SQL。

REPLACE PROCEDURE Demo()
DYNAMIC RESULT SETS 1 -- SP will return a result set
BEGIN 
   Declare REnd Date;
   Declare RStart Date;

   Set REnd = (select max(CalendarDate) as REnd 
               from Table1 
               where CalendarDate = MonthEndDate
               and  Monthofyear in ('June', 'December')
               and CalendarDate < Current_date()
              );

   Set RStart = (select max(CalendarDate) as RStart
               from Table1 
               where CalendarDate = (CalendarDate - Extract(Day From CalendarDate)+1)
               and  Monthofyear in ('January', 'July')
               and CalendarDate < REnd
              );

   -- Return result set
   BEGIN
      DECLARE cur2 CURSOR WITH RETURN ONLY FOR
       -- this is your query using parameters
         select * from table2 
         where reviewdate between :RStart and :REnd;

      OPEN cur2; -- don't close, otherwise no result set
   END;
END;

游標對於處理數據來說是邪惡的，但這不是真正的 cursor，它只是用於返回結果集的冗長的標准 SQL 語法:-)