database - 为什么 Firebird 的存储过程中不允许使用临时表？

Question

我正在尝试在 Firebird 数据库的存储过程中创建临时表。

我的存储过程 list :

SET TERM ^ ;

CREATE PROCEDURE initNATIONALHEALTHFUNDS
 
AS BEGIN

  CREATE GLOBAL TEMPORARY TABLE temp_FUNDS 
  (
    NATIONALHEALTHFUNDID Integer NOT NULL,
    NAME Varchar(128) NOT NULL,
    CODE Integer NOT NULL
  )
  ON COMMIT PRESERVE ROWS;
  commit;
  
 INSERT INTO tempFUNDS (NATIONALHEALTHFUNDID, CODE, NAME)  VALUES ( 01 ,01 , 'Some Foundation');

    
  MERGE INTO NATIONALHEALTHFUNDS  AS target 
   USING tempFUNDS AS source 
   ON target.NATIONALHEALTHFUNDID = source.NATIONALHEALTHFUNDID
   WHEN NOT MATCHED THEN 
    INSERT (NATIONALHEALTHFUNDID, CODE, NAME) VALUES (source.NATIONALHEALTHFUNDID, source.CODE, source.NAME);
    
  drop  TABLE tempFUNDS;
END^

SET TERM ; ^

每次我尝试创建这个程序时，我都会收到错误消息:

    Engine Code    : 335544569
Engine Message :
Dynamic SQL Error
SQL error code = -104
Token unknown - line 7, column 3
CREATE


Total execution time: 0.015s

我做错了什么？我正在使用 Firebird 3.0 RC

Answer 1

Firebird 不允许您在存储过程中使用 DDL，因此 CREATE 语句在 PSQL 中是不允许的。如 answer by lad2025 中所示您可以使用 EXECUTE STATEMENT 解决此限制.

然而，global temporary table背后的想法是你创建一次，它们继续存在，以便以后使用。数据仅对创建数据的连接可见，数据在事务提交(ON COMMIT DELETE ROWS)或连接关闭(ON COMMIT PRESERVE ROWS)后删除取决于全局临时表的类型。

来自 Firebird 3.0 语言引用:

Global temporary tables have persistent metadata, but their contents are transaction-bound (the default) or connection-bound. Every transaction or connection has its own private instance of a GTT, isolated from all the others. Instances are only created if and when the GTT is referenced. They are destroyed when the transaction ends or on disconnection.

因此，与其尝试在存储过程中创建全局临时表，不如先创建它，然后再创建使用已定义的 GTT 的存储过程。