AdapTable follows a series of steps when it wants to provide a list of values for a column (e.g. in a column filter, or when building a query or in Bulk Update).
It will first look for any Permitted Values for that column, set via the permittedValues property in UserInterface Options - where you can provide either a list or a function.
Here we set 4 Permitted Values:
A 'hard-coded' set of Values for Contact and Employee columns - so only this list of values is displayed in their Column Filters (and Expression Editor).
 For Cust Ref. column a function that will be evaluated each time the list is required; this allows you to get the values from your local store or via an external look-up.
An empty array [' '] for the Order Date Column so that NO distinct column values are diplayed, and only the System Filters for Date columns are shown.
Note: if there are no Permitted Values provided, then AdapTable will dynamically build a list of current distinct values for the column.