Re: Multiple Inputs on an operation

[Jason Meckley]

using a single db input command per query and a join operation to merge them together.

On Friday, June 15, 2012 9:32:25 AM UTC-4, John Strzempa wrote:

Hello,

How can I use multiple select statements per process. I have a get products operation that selects all the products from source database but I also want to query the destination database and use the rows there throughout the process for comparing etc... Would I just add to the already selected rows?

[John Strzempa]

What if it's data from an unrelated table but you still want to look at some of it's data throughout the process? Can I just add to the row somehow? Is there a right way to do this?

[Jason Meckley]

ETL is about processing Rows (in memory objects), where the rows come from doesn't matter. Joins occur in memory allowing you to relate disjointed data. So whether the table is unrelated doesn't apply in the scope of the ETL process. here is an example of what I mean. And this is all off the top of my head.

Initialize()

{

   Register(new MyLeftJoinOperation()

                                  .Left(new GetDataFromHere())

                                  .Right(new MyInnerJoinOperation()

                                                      .Left(new GetDataFromThere())

                                                      .Right(Partial

                                                                  .Add(new GetDataFromYetAnotherPlace())

                                                                  .Add(new TransformBeforeJoining()) 

                                   )));

   Register(new TransformRows());

   Register(new SendDataOut());

}

My guess is you will need to use a combination of Nested Join operations and the PartialProcessOperation.

[John Strzempa]

Thanks,

I'll have to try a couple more things. I guess I thought because it was a join, you had to join it to something related in both tables but it sounds like you're saying you do not so that is something I'll have to get used to.

[Jason Meckley]

Don't think it terms of tables, think in terms of dynamic objects (called Rows in Rhino.ETL) yes you will need to join the row object together, but that join is independent of where the data comes from.