topic Re: tmap cross join question in Talend Studio

tmap cross join question

Anonymous — Tue, 30 Apr 2019 15:18:15 GMT

From the screenshot i don't see any link between row1 and row2 in tmap. what kind of join is this? so far I saw a join condition(inner join) and a link. In this case it says left outer join but on what condition is the big question. From what i see my data does not match on those columns. Even if this is a cross join there should be a matching condition but in this case there is none. I am having hard time trying to decode this to Sql. Any help on this is greatly appreciated.

Re: tmap cross join question

David_Beaty — Tue, 30 Apr 2019 15:45:12 GMT

Hi,

Its giving you the Cartesian product of both sources. The "Left outer join" is part of the join model, which you have no join, so is somewhat obsolete. For each individual flow in row1.....every entry in row2 will be matched.

Re: tmap cross join question

Anonymous — Tue, 30 Apr 2019 15:48:08 GMT

Thank you very much. This helps.

Re: tmap cross join question

Anonymous — Tue, 30 Apr 2019 16:00:07 GMT

A tMap is driven by one input source, the main source. In your case that is row1. Any other source is just for lookups. If you are not joining, then you will get every row of the lookup "matched" against every row of the main IF "Match Model" is set to "All rows". What you have there does look like a cross-join. You do not need a join condition on a cross-join as it is the Cartesian product.

Re: tmap cross join question

Anonymous — Tue, 30 Apr 2019 16:02:12 GMT

Sorry @dsoulalioux, it appears I started my response before you started yours and then got involved in something else before posting 🙂 Nice answer