how to perform self join

[ksk]

Hi,

How to perform self join using join stage in parallel
is it possible to perform a self join.

Thanks

[Magesh_bala]

Hi,

I think you need to use the same file as right and left. then you can achive the self join in datastage.

[ksk]

Hi,

I think you need to use the same file as right and left. then you can achive the self join in datastage.

Is it possible do with a single input file ?

[ray.wurlod]

Yes, both the Join stage inputs read data from the same file.

[ksk]

Yes, both the Join stage inputs read data from the same file. ...

i want to use only one input stage not two same input stage for example

[Sainath.Srinivasan]

You can always include something like a copy and stream them into two.

[truenorth]

i want to use only one input stage not two same input stage for example

But a join requires two input streams.

[ray.wurlod]

Yes. And your point is?

Code: Select all

                        +----------------+
                        |                V
      SeqFile  ---->  Copy              Join  -------> 
                        |                ^
                        +----------------+

[truenorth]

I understand the OP to mean he only wants one input into a Join stage, which requires two. So to do a self-join, I'm with you...two inputs, but both are the one physical input.

[chulett]

No, they stated "one input stage" not one input into the Join, which (as noted) is not possible. And that solution has been posted. More than once.

[battaliou]

You're probably better off landing your data into a dataset, and depending on volumes using a lookup or joining the data in a second job. Of course if you insist on using only 1 input stream, you could copy this into 2 sorts based on the join keys and merge your data together. This will have rubbish results if your join key is not unique.