Select All as default value for Multivalue parameter

Does not work if you have nulls.

You can get around this by modifying your select statement to plop something into nulls:

phonenumber = CASE
  WHEN (isnull(phonenumber, '')='') THEN '(blank)'
  ELSE phonenumber
END

Try setting the parameters' "default value" to use the same query as the "available values". In effect it provides every single "available value" as a "default value" and the "Select All" option is automatically checked.

Using dataset with default values is one way, but you must use query for Available values and for Default Values, if values are hard coded in Available values tab, then you must define default values as expressions. Pictures should explain everything

Create Parameter (if not automaticly created)

Define values - wrong way example

Define values - correct way example

Set default values - you must define all default values reflecting available values to make "Select All" by default, if you won't define all only those defined will be selected by default.

The Result

One picture for Data type: Int