I usually do things like this using workflow because even if you could group the data together you still need html or something to format it cleanly in the email.

Typically, I would have a workflow in which I create a multi value token for the rows, then I use Retrieve Business Process Variables to retrieve the table.

Next, I'd use a For Each Row activity to iterate over each row of the table, build the html string using the current values, and append the data to the multivalue token created earlier.

For example, if you are using an HTML table you would do something like

<tr><td>%(ForEachRow_Column1)</td><td>%(ForEachRow_Column2)</td></tr>

Then in your email, you can plug your multivalue token into the email and flatten the values (use the token editor, select "all values separated by" and leave it blank).

FYI,

Here is your main email text

<table><tbody>%(RowsToken#[]#)</tbody></table>