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