Merge vs Union All transformations

Differences between Merge and Union All transformations in SSIS

S.No	Merge	Union All
1	Number of inputs allowed: Merge transformation can accept only two inputs.	Number of inputs allowed: Union all can take more than two inputs.
2	Data to be sorted or not before Merge transformation: Data has to be sorted before Merge Transformation.	Data to be sorted or not before Union All transformation: Union all does not have any condition like Merge.

For illustration, please visit @

http://sqljoe.wordpress.com/2011/03/03/differences-between-merge-and-unionall-transformations-in-ssis/

Summary: Both of them essentially takes outputs from more than one sources and combines them into a single result set.