How to merge data retrieved from multiple DBs

Question

I would like to merge data retrieved from multiple DBs.
What operations should I use for this purpose?

Answer

For example, here are the ways to merge 3 different input data.

1. Place multiple Join operations
   After merging two pieces of data using a Join operation, merge the resulting output data and the unmerged data using another Join operation.
   
   Join
   https://www.hulft.com/help/en-us/HULFTSquare/Content/Designer/Connector/basic_join.htm
   
   
2. Use Merge Mapper
   Merge Mapper allows you to specify multiple pieces of input data.
   You can merge output data from multiple components by specifying them as input for the Mapper.
   
   Merge Mapper
   https://www.hulft.com/help/en-us/HULFTSquare/Content/Designer/Mapper/mpp_mm_detail.htm
   
   

It is recommended to use Join operation when possible because Join operation is a function to improve the performance of Merge Mapper.

However, please note that Join operation cannot use XML type as input data unlike Merge Mapper.