What are the differences between Merge Join and Lookup transformations in SSIS?

Question

Hi I\'m new to SSIS packages and writing a package and reading up about them at the same time.

I need to convert a DTS into a SSIS package and I need to perform a j

Answer 1

A Merge Join is designed to produce results similar to how JOINs work in SQL. The Lookup component does not work like a SQL JOIN. Here's an example where the results would differ.

If you have a one-to-many relationship between input 1 (e.g., Invoices) and input 2 (e.g., Invoice Line Items), you want the results of the combining of these two inputs to include one or more rows for a single invoice.

With a Merge Join you will get the desired output. With a Lookup, where input 2 is the look up source, the output will be one row per invoice, no matter how many rows exist in input 2. I don't recall which row from input 2 the data would come, but I'm pretty sure you will get a duplicate-data warning, at least.

So, each component has its own role in SSIS.