coll.union

Description

Combines two lists and returns a new list containing all unique elements from both lists. Duplicates are automatically removed, treating the inputs as sets.

Syntax 

flex.coll.union(list1, list2)

Parameters

| Parameter | Type | Required | Description | |———–|——|———-|————-| | list1 | list | Yes | The first list | | list2 | list | Yes | The second list |

Returns

Type: list

A new list containing all unique elements from both input lists. The order is not guaranteed.

Examples

Example 1: Basic Union 

WITH [1, 2, 3] AS a, [3, 4, 5] AS b
RETURN flex.coll.union(a, b) AS result

Output:

result
--------------
[1, 2, 3, 4, 5]

Example 2: Combining Tags from Multiple Nodes 

MATCH (d1:Document {id: 'doc1'})
MATCH (d2:Document {id: 'doc2'})
RETURN flex.coll.union(d1.tags, d2.tags) AS allTags

Example 3: Merging User Interests 

MATCH (u:User)
WITH collect(u.interests) AS interestLists
RETURN reduce(result = [], list IN interestLists | 
    flex.coll.union(result, list)
) AS allUniqueInterests

MATCH (p:Product {id: 123})
MATCH (similar:Product)-[:SIMILAR_TO]-(p)
RETURN flex.coll.union(p.categories, similar.categories) AS combinedCategories

Notes

  • Automatically removes duplicates from the result
  • Works with any comparable data types
  • Order of elements in the result is not guaranteed
  • Equivalent to mathematical set union operation
  • Both lists are spread and deduplicated using Set

See Also