Merge and Merge Join Task

What are the purpose for Mer开发者_JAVA技巧ge and Merge join Tasks in Data Flow ?

I think the merge task is like doing a union in a sql query whereas a merge join is like doing an Inner/Left join in SQL

it combines to paths in the data flow, you can choose which columns to merge together, so if you have two data sources and you want to combine, you can merge on columns and come out with one output, and insert that output or put it to a flat file, for example, instead of writing two output.