Before diving into using Supabase functions to transform data on the fly, make sure you've got these bases covered:

• You need an active Supabase account and a project set up.
• You should know the basics of running SQL commands in the Supabase dashboard.
• A bit of JavaScript knowledge is handy since Supabase functions are written in JavaScript.

First things first, let's create a new function in Supabase. Head over to the SQL tab in the dashboard and type out a CREATE FUNCTION command in SQL.

CREATE OR REPLACE FUNCTION my_function_name()
  RETURNS trigger AS
$func$
BEGIN
  -- function logic goes here
  RETURN NEW;
END
$func$ LANGUAGE plpgsql;

Swap out "my_function_name" with whatever you want to call your function. You can also change "trigger" if you need a different return type, but for most data transformations, "trigger" works just fine.

Now that you've got your function set up, it's time to add the transformation logic. Supabase functions use PL/pgSQL, which is pretty close to SQL.

Say you want to convert all text entries in a column to uppercase. Your function might look like this:

CREATE OR REPLACE FUNCTION make_uppercase()
  RETURNS trigger AS
$func$
BEGIN
  NEW.my_column = UPPER(NEW.my_column);
  RETURN NEW;
END
$func$ LANGUAGE plpgsql;

Just replace "my_column" with the name of the column you want to change.

With your function ready and the logic in place, the next step is to set up a trigger. This trigger will make sure your function runs whenever a specific event happens in your database.

To create a trigger, use the CREATE TRIGGER command. Here's an example:

CREATE TRIGGER my_trigger_name
  BEFORE INSERT OR UPDATE ON my_table_name
  FOR EACH ROW EXECUTE FUNCTION make_uppercase();

This trigger will run the "make_uppercase" function before each insert or update on "my_table_name". Just replace "my_trigger_name" and "my_table_name" with your chosen names.

Now, whenever an INSERT or UPDATE happens on your specified table, the trigger will automatically call your function to transform the data before it's saved.

Using Supabase functions like this makes it a breeze to handle data transformation on-the-fly, keeping your database efficient and your data consistent.