如何在Teradata SQL宏中使用变量 [英] How to use variables in Teradata SQL Macros

问题描述

我想在Teradata的宏SQL中使用变量.

I'm wanting to use variables inside my macro SQL on Teradata.

我认为我可以做以下事情:

I thought I could do something like the following:

REPLACE MACRO DbName.MyMacro  
(  
   MacroNm   VARCHAR(50)  
)  
AS  
(  

   /* Variable to store last time the macro was run */  

   DECLARE V_LAST_RUN_DATE TIMESTAMP;  


   /* Get last run date and store in V_LAST_RUN_DATE */  

   SELECT LastDate  
   INTO V_LAST_RUN_DATE  
   FROM DbName.RunLog  
   WHERE MacroNm = :MacroNm;  


   /* Update the last run date to now and save the old date in history */  

   EXECUTE MACRO DbName.RunLogUpdater(  
      :MacroNm  
     ,V_LAST_RUN_DATE  
     ,CURRENT_TIMESTAMP  
   );  

);  

但是，那没有用，所以我想到了:

However, that didn't work, so I thought of this instead:

REPLACE MACRO DbName.MyMacro  
(  
   MacroNm   VARCHAR(50)  
)  
AS  
(  

   /* Variable to store last time the macro was run */  

   CREATE VOLATILE TABLE MacroVars AS  
   (  
         SELECT  LastDate AS V_LAST_RUN_DATE  
           FROM  DbName.RunLog  
          WHERE  MacroNm = :MacroNm;  
   )  
   WITH DATA ON COMMIT PRESERVE ROWS;  


   /* Update the last run date to now and save the old date in history */  

   EXECUTE MACRO DbName.RunLogUpdater(  
      :MacroNm  
     ,SELECT V_LAST_RUN_DATE FROM MacroVars  
     ,CURRENT_TIMESTAMP  
   );  

);  

我可以使用存储过程来完成所需的工作，但是我想避免这种情况.

I can do what I'm looking for with a Stored Procedure, however I want to avoid for performance.

您对此有任何想法吗?
还有什么我可以尝试的吗?

Do you have any ideas about this?
Is there anything else I can try?

干杯
蒂姆

推荐答案

您不能在宏内部声明变量.如果您愿意，可以使用UPDATE语句来处理您要完成的任务.

You can't DECLARE a variable inside of a macro. What you are trying to accomplish could be handled with an UPDATE statement if you so choose.

UPDATE TGT
FROM <dbname>.<target table> TGT
   , (SELECT MacroName
           , LastRunDate
      FROM <dname>.<source table>
     ) SRC
SET LastRunDate = SRC.LastRunDate
  , EffectiveTimestamp = CURRENT_TIMESTAMP(0)
WHERE TGT.MacroName = SRC.MacroName
;

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