Parameters are special M queries that do not access an external data source and only return a scalar or individual value, such as a specific date, number, or string of text characters. The primary use case for parameters is to centrally define a common and important value, such as a server name or the name of a database, and then reference that parameter value in multiple other queries. Like global variables, parameters improve the manageability of large datasets as the dataset designer can simply revise a single parameter's value rather than manually modify many queries individually.
Query parameters can be created and modified via the Manage Parameters dialog available on the Home tab of the Power Query Editor. The ...
