Lost value of a constant

Question

In the spec part of a package I define
c_GTCON50_S CONSTANT VARCHAR2(1):='S';
In a procedure in the body part I do:
INSERT INTO IGIC_DECE_400_11_INCIDENCIAS
( ID_DECE_INCI, ID_DECE_400, COD_DECE_INCI,
COD_DECE_NIVI, ACTIVA_INCIDENCIA,
FECHA_INICIO_SIT_TRIB, FECHA_FIN_SIT_TRIB )
VALUES
( GTSEQU_INCI.nextval, p_id_DECE400, p_incidencia,
p_codDeceNivi, c_GTCON50_S, NULL, NULL );
Do you see? I INSERT that constant... But when I inspect what I have in the table, I can see that record but the field corresponding to the constant IS NULL ??????
Why?
What's the reason for that "lost value" of a constant?
This procedure of the package with that INSERT is executed by another package..
I don't know if it is a clue...
Edited by: pacoKAS on 31-mar-2010 14:13

Answer 1

pacoKAS wrote:
Thank you for your interest...
But my CONSTANT is ONLY defined in the specification section of the package.... The "invoking" package has not defined a CONSTANT with the same name....A constant cannot be changed.
SQL> create or replace package MyLibrary is
  2
  3          MY_CONSTANT     constant varchar2(5) := 'fixed';
  4
  5  end;
  6  /
Package created.
SQL>
SQL>
SQL> -- cannot change its value
SQL> exec MyLibrary.MY_CONSTANT := 'gotya';
BEGIN MyLibrary.MY_CONSTANT := 'gotya'; END;
ERROR at line 1:
ORA-06550: line 1, column 17:
PLS-00363: expression 'MYLIBRARY.MY_CONSTANT' cannot be used as an assignment target
ORA-06550: line 1, column 7:
PL/SQL: Statement ignored
SQL>
There is a reason for the "loss of value" of the constant...
But I don't know that reason....It cannot loose the value. Not possible. As shown above, you cannot change the variable's value - the reserve word "+constant+" does not allow it.
The only other explanation is scope - you think you are referring to that constant, but within the current code unit's scope, the reference is to another variable. And that's the value that you see.
This is of course assuming that you are diagnosing the problem correctly. A trigger could be responsible for changing the row's column value set by that constant via the INSERT statement. There could be an error (constraint violation for example) that is suppressed - so it seems that a row with that constant value is inserted, when it is not the case. Etc.