Oracle considers empty strings to be NULL while SQL Server does not - how is this best handled?

Question

I have to write a component that re-creates SQL Server tables (structure and data) in an Oracle database. This component also has to take new data entered into the Oracle d

Answer 1

Although, for the most part, I agree with most of the other responses (not going to get into an argument about any I disagree with - not the place for that :) )

I do notice that OP mentioned the following:

"Oracle considers a blank string to be the same as a NULL value, so if a char column is defined as NOT NULL, you cannot insert a blank string."

Specifically calling out CHAR, and not VARCHAR2. Hence, talking about an "empty string" of length 0 (ie '' ) is moot. If he's declared the CHAR as, for example, CHAR(5), then just add a space to the empty string coming in, Oracle's going to pad it anyway. You'll end up with a 5 space string.

Now, if OP meant VARCHAR2, well yeah, that's a whole other beast, and yeah, the difference between empty string and NULL becomes relevant.

  SQL> drop table junk;

  Table dropped.

  SQL>
  SQL> create table junk ( c1     char(5) not null );

  Table created.

  SQL>
  SQL> insert into junk values ( 'hi' );

  1 row created.

  SQL>
  SQL> insert into junk values ( ' ' );

  1 row created.

  SQL>
  SQL> insert into junk values ( '' );
  insert into junk values ( '' )
                            *
  ERROR at line 1:
  ORA-01400: cannot insert NULL into ("GREGS"."JUNK"."C1")


  SQL>
  SQL> insert into junk values ( rpad('', 5, ' ') );
  insert into junk values ( rpad('', 5, ' ') )
                            *
  ERROR at line 1:
  ORA-01400: cannot insert NULL into ("GREGS"."JUNK"."C1")


  SQL>
  SQL> declare
    2    lv_in   varchar2(5) := '';
    3  begin
    4     insert into junk values ( rpad(lv_in||' ', 5) );
    5  end;
    6  /

  PL/SQL procedure successfully completed.

  SQL>