Firebird constant value

Question

Is it possible to have database wide constants? What I want is to define a constant like:

• UPDATE_CONSTANT = 1
• INSERT_CONSTANT = 2
• DELETE_CONSTANT = 3

and then use it in for example a trigger like:

CREATE TRIGGER AD_PRJ_PROJECTS FOR PRJ_PROJECT
ACTIVE AFTER DELETE
POSITION 1
AS
BEGIN
   EXECUTE PROCEDURE SP_ADD_HISTORY 'PRJ_PROJECT', DELETE_CONSTANT;
END;

Answer 1

You could use a generator:

SET GENERATOR DELETE_CONSTANT TO 3;

...

EXECUTE PROCEDURE SP_ADD_HISTORY 'PRJ_PROJECT', GEN_ID(DELETE_CONSTANT, 0);

Answer 2

I don't think there is an easy way for declaring constants.

I could be done by creating you own DLL for user defined function, and lmake a function for each constant.

I Think the Idea using generators as "global" constants is briliant.

But you can make a "local constant" to make your code a bit more readable:

CREATE TRIGGER AD_PRJ_PROJECTS FOR PRJ_PROJECT
ACTIVE AFTER DELETE
POSITION 1
AS
  DECLARE VARIABLE DELETE_CONSTANT INTEGER;
BEGIN
   DELETE_CONSTANT = 1;
   EXECUTE PROCEDURE SP_ADD_HISTORY 'PRJ_PROJECT', DELETE_CONSTANT;
END;