List.Union Function in Power Query

The List.Union function returns a list from a list of lists and unions the items in the individual lists. The returned list contains all items in any input lists. In this function at the time of merging the lists the duplicates are removed. It is different from the List.Combine function where at the time of merging the list the duplicates are retained.

Syntax

List.Union(lists as list, optional equationCriteria as any) as list

The function has the following parameters:
• lists: A list of lists to be combined.
• equationCriteria (Optional): Specifies how to compare values for duplicates (e.g., case sensitivity). Defaults to Comparer.Ordinal (case-sensitive).

Example: Create a union of list in power query.

Power Query M

let
  list1  = {"Ashish", "Esha", "Katrina"},
  list2  = {"Samyukta", "Esha", "Jennifer"},
  list3  = {"Alia", "Warina", "Katrina"}, 
  return = List.Union({list1, list2, list3})
in
  return

The output of the above code is shown below:

Comparison to Related Functions The following are some related functions:

List Function	Behavior
List.Union	Combines lists and removes duplicates.
List.Combine	Combines lists without removing duplicates.
List.Distinct	Removes duplicates from a single list.
List.Intersect	Returns common values between lists.

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