Unnesting consists of converting a list of objects into rows, each row containing an item of the list. It is the exact opposite of COLLECT, which groups objects together into a list.
With Cypher, we will use the following statement:
UNWIND
For instance, the following two queries are equivalent:
MATCH (:State {code: "FL"})-[:SHARE_BORDER_WITH]-(n)
WITH COLLECT(n.code) as codes
UNWIND codes as c
RETURN c
// is equivalent to, since COLLECT and UNWIND cancel each other:
MATCH (CO:State {code: "FL"})-[:SHARE_BORDER_WITH]-(n)
RETURN n.cod
This returns our well-known two state codes.
The UNWIND operation will be useful for data imports, since some files are formatted in a way that several pieces of information can be aggregated on a single row. Depending on the data format, this function can be useful when importing data into Neo4j, as we will see in the next section.
