Using the Power Query Add-In - Microsoft Business Intelligence Tools for Excel Analysts - page 141

Power Query saves the data source parameters for each data source connection you have used. You
can view, edit, or delete any of the data source connections by clicking the Data Source Settings
button on the Power Query tab. In the Data Source Settings dialog box, select any connection and
you can edit or delete it; see Figure 7-16.

Figure 7-16: The Data Source Settings dialog box enables you to edit or delete previously used data
connections.

Deleting a connection does not delete any of its associated data you may have already
loaded in your workbook or internal Data Model. However, when you try to refresh the
data, Power Query won't have any of the connection parameters (because you deleted
them), so it asks you again for the connection parameters.

Note

Creating and Using Power Query Functions
Earlier in this chapter, we discussed how Power Query uses its own formula language known as M.
When you connect to a data source and apply transformations to that data, Power Query diligently
saves your actions as M code behind the scenes in query steps. This allows for your transformation
steps to be repeated when you refresh the data in your query.

With a little knowledge, you can leverage the M language to extend the capabilities of Power Query
with your own custom functions. Custom functions come in handy when you frequently need to
apply business-specific calculations or perform complex transformations involving conditional test-
ing with If . . . Then . . . Else logic.

In this section we walk you through the basics of building your own custom functions.