How to get null when use head funtion with a empty list in cypher?
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Published on 2012-10-23T05:29:03Z
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I have a cypher query like this.
START dep=node:cities(city_code = "JGS"),
arr=node:cities(city_code = "XMN")
MATCH dep-[way:BRANCH2BRANCH_AIRWAY*0..1]->()-->arr
RETURN length(way), transfer.city_code,
extract(w in way: w.min_consume_time) AS consumeTime
The relationship named "way" is a optional one, so the property named "consumeTime" will be a empty list when the relationship "way" not exsit.
The query result is:
| 0 | "JGS" | [] |
| 1 | "SZX" | [3600] |
When I want to use the head function with the property "consumeTime", it return a error "Invalid query: head of empty list".
How can I get a result like this?
| 0 | "JGS" | null |
| 1 | "SZX" | 3600 |
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