Data Transformation

How can I aggregate columns of a dataset by a function (mean, min, etc.)?

The table operator has built-in functionality for several aggregation functions. If you want to do something more complex, consider using a user-defined operator.

How do I get the frequency counts of a column in a table?

Select your column in the "group" menu, then pick the "count" aggregation method for that column in the "attributes" menu of the table. See the Table page for more details.

I want to change the SQL query for a dataset in a canvas. How can I do that?

The SQL dataset operator allows you to do this.