Mithun Ganguly

• Sep 14th, 2005

 

An outer join is used when one wants to select all the records from a port - whether it has satisfied the join criteria or not.

K Nagi Reddy

• May 4th, 2006

 

If you want to see all the records of one input file independent of whether there is a matching record in the other file or not. then its an outer join.

pedro

• Jan 13th, 2007

 

Just to complete the remaining considerations.

The outer join, just like the explicit semi joins, will assign null to the non existing fields that should be assigned  by the non existing flows. Therefore lookout for non-nullable fields.