You will need to relate the data between the two sources to create a link (also known as a relationship or a JOIN). This url should help explain the steps in tableau:
The comma list, is a comma delimited list, you should import it into excel and make sure that each field is in the correct amount of columns. You can google "import excel comma delimited list", and that should give you some examples of what you need to do. In general your data should be as clean as you can get it before you consider connecting it to Tableau, my suggestion would be to clean it up (import the delimited list) using Excel if you are more familiar with Excel than Tableau.
I can do that in excel.
I tried to join both data in Tableau but somehow Tableau deleted the row that doesn't contain a common field. Is there anyway to keep all the fields?
I'm not exactly sure what you are trying to ask, but the data you are importing sounds like it should be 2 data sources, and have a relationship using the common field, you should have all the fields available, if its numeric you might want to look to see if it got automatically defined as a measure and not as a dimension.
You might want to look around on how to combine multiple data sources to get an idea of where things could be going wrong.
You can use the data sets Tableau provides to practice with first to make sure you aren't missing a step when importing the data and making the connection between the multiple data sources/data sets.