How to create trigger in informix?

Question

I am trying to write a trigger like in the following simplified example:

create trigger adr_trg update of fname, lname on adr
REFERENCING OLD AS o NEW AS n
FOR EACH ROW
(
  IF o.fname <> n.fname THEN
    insert into adrlog (old_value, new_value)
    values (o.fname, n.fname);
  END IF;

  IF o.lname <> n.lname THEN
    insert into adrlog (old_value, new_value)
    values (o.lname, n.lname);
  END IF;
)

This fails!

Only this works:

create trigger adr_trg update of fname, lname on adr
REFERENCING OLD AS o NEW AS n
FOR EACH ROW
(
    insert into adrlog (old_value, new_value)
    values (o.fname, n.fname);
)

What am I doing wrong?

Solution 1

I think you should write a stored procedure with the IF - THEN logic and call that from this trigger. I think triggers support only simple SQL statements, not SPL statements

edit:

CREATE PROCEDURE proc1()
REFERENCING OLD AS o NEW AS n FOR tab1; 
....your logic


CREATE TRIGGER adr_trg update of fname, lname on adr
REFERENCING OLD AS o NEW AS n
  FOR EACH ROW(EXECUTE PROCEDURE proc1() WITH TRIGGER REFERENCES);

Solution 2

Old question, but not well answered, in case anyone lands up here like I did.

Informix handles the requested functionality, but the syntax is different:

create trigger adr_trg update of fname,lname on adr 
 referencing old as o new as n
    for each row
    when ( o.fname != n.fname )
    (
      insert into adrlog (old_value,new_value)
        values (o.fname,n.fname)
    ) ,
    when ( o.lname != n.lname )
    (
      insert into adrlog (old_value,new_value)
        values (o.lname,n.lname)
    )
;

Comments

[RET]

A good tradesman never blames his tools. It seems to me that the conditional logic you require is best placed in a procedure. It may prove to be sufficiently generic that it can be used for multiple tables, in an OO fashion. Your simplified example certainly suggests this.

[Lukas Eder]

For the reference, here's the relevant manual page