Question

I have an oralcle SP forced on me that will not accept an empty parameter in an update. So if I wanted to set a value back to the default of (”) it will not let me pass in the empty string. Is there a keyword you can use such as default, null, etc that oracle would interpret back to the default specified for a particular column?

Answer 1

Sometimes things are just as simple as you hope they might be.

First, a table with a default value …

SQL> create table t23 (
  2      id number not null primary key
  3      , col_d date default sysdate not null )
  4  /

Table created.

SQL> insert into t23 values (1, trunc(sysdate, 'yyyy'))
  2  /

1 row created.

SQL> select * from t23
  2  /

        ID COL_D
---------- ---------
         1 01-JAN-10

SQL>

Next a procedure which updates the default column …

SQL> create or replace procedure set_t23_date
  2      ( p_id in t23.id%type
  3        , p_date in t23.col_d%type )
  4  is
  5  begin
  6      update t23
  7      set col_d = p_date
  8      where id = p_id;
  9  end;
 10  /

Procedure created.

SQL>

… but which doesn’t work as we would like:

SQL> exec set_t23_date ( 1, null )
BEGIN set_t23_date ( 1, null ); END;

*
ERROR at line 1:
ORA-01407: cannot update ("APC"."T23"."COL_D") to NULL
ORA-06512: at "APC.SET_T23_DATE", line 6
ORA-06512: at line 1


SQL>

So, let’s try adding a DEFAULT option …

SQL> create or replace procedure set_t23_date
  2      ( p_id in t23.id%type
  3        , p_date in t23.col_d%type )
  4  is
  5  begin
  6      if p_date is not null then
  7          update t23
  8          set col_d = p_date
  9          where id = p_id;
 10      else
 11          update t23
 12          set col_d = default
 13          where id = p_id;
 14      end if;
 15  end;
 16  /

Procedure created.

SQL>

… and lo!

SQL> exec set_t23_date ( 1, null )

PL/SQL procedure successfully completed.

SQL>
SQL> select * from t23
  2  /

        ID COL_D
---------- ---------
         1 28-FEB-10

SQL>

I ran this example on an 11g database. I can’t remember when Oracle introduced this exact support for DEFAULT, but it has been quite a while (9i???)

edit

The comments are really depressing. The entire point of building PL/SQL APIs is to make it easier for application developers to interact with the database. That includes being sensible enough to rewrite stored procedures when necessary. The big difference between building something out of software and, say, welding cast-iron girders together is that software is malleable and easy to change. Especially when the change doesn’t alter the signature or behaviour of an existing procedure, which is the case here.