When we go for unconnected lookup transformation? and why?

Question

In unconnected lookup, what are the other transformations that can be used in place of that expression transformation?

Answer 1

If u want to use the same look up T/R more than one time,you should use compulsory Unconnected lookup.A common use for unconnected Lookup transformations is to update slowly changing dimension tables.I know these 2 uses.

OR

1. Calling the same lookup multiple times in one mapping

2. Testing the results of a lookup in an expression

3. Filtering rows based on the lookup results

4. Marking rows for update based on the result of a lookup,
   such as updating slowly changing dimension tables