ub

• Jun 7th, 2006

 

join can have max of two input datasets, Merge can have more than two input datesets.

Unknown

• Jun 8th, 2006

 

Merge and Join Stage Difference :

1. Merge Reject Links are there

2. can take Multiple Update links

3. If you used it for comparision , then first matching data will be the output .

Because it uses the update links to extend the primary details which are coming from master link

Alok Ranjan

• Jun 8th, 2006

 

Someone was saying that join does not support more than two input , while merge support two or more input (one master and one or more update links). I will say, that is highly incomplete information. The fact is join does support two or more input links (left right and possibly intermediate links). But, yes, if you are tallking about full outer join then more than two links are not supported.

Coming back to main question of difference between Join and Merge Stage, the other significant differences that I have noticed are:

1) Number Of Reject Link

(Join) does not support reject link.

(Merge) has as many reject link as the update links( if there are n-input links then 1 will be master link and n-1 will be the update link). 

2) Data Selection

(Join) There are various ways in which data is being selected. e.g. we have different types of joins, inner, outer( left, right, full), cross join, etc. So, you have different selection criteria for dropping/selecting a row.

(Merge) Data in Master record and update records are merged only when both have same value for the merge key columns.

-----Please share if someone is aware of more differences -----