Re: joining on columns with null value

Works for me:

create table t1 (a number, b number, c varchar2(10));
insert into t1 values (1,1,'A');
insert into t1 values (1,null,'A');
insert into t1 values (1,2,'A');
insert into t1 values (2,1,'B');
insert into t1 values (2,null,'B');
insert into t1 values (2,2,'B');
commit;
create table t2 as select * from t1;
select t1.*, t2.* from t1, t2
where t1.a = t2.a
and t1.b = t2.b;

   A   B C    A   B C
--- --- -- --- --- --
   1   1 A    1   1 A
   1   2 A    1   2 A
   2   1 B    2   1 B
   2   2 B    2   2 B

select t1.*, t2.* from t1, t2
where t1.a = t2.a
and nvl(t1.b,0) = nvl(t2.b,0);

   A   B C    A   B C
--- --- -- --- --- --
   1     A    1     A
   1   1 A    1   1 A
   1   2 A    1   2 A
   2     B    2     B
   2   1 B    2   1 B
   2   2 B    2   2 B

Of course, you want to use a value in the nvl which is guaranteed NOT to 
occur as a real non-null value.



ryan_gaffuri@xxxxxxxxxxx wrote:
> I have to join two tables. all of the columns can be null. However, if there 
> are nulls and the rest of the fields are the same, I want to join to 
> succeed.I did a test case where i assumed that if i used the following, I 
> would get a record returned even if there are nulls. 
> where nvl(tableA.column,0) = nvl(tableB.column,0)
> 
> If both of these fields are null and i have the rest of the columns 
> equivalent, this will not give me a record returned. 
> 
> However, if i do:
> 
> where tableA.column1||tableA.column2||tableA.column3 = 
> tableB.column1||tableB.column2||tableB.column3
> 
> then i get a successful join if one or more of the fields is null but atleast 
> 1 is not. 
> this is pretty ugly. Any better way to do this? 
> 
> --
> http://www.freelists.org/webpage/oracle-l
> 

-- 
Regards

Wolfgang Breitling
Centrex Consulting Corporation
www.centrexcc.com
--
http://www.freelists.org/webpage/oracle-l

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