How to get null when use head funtion with a empty list in cypher?
Posted
by
PeaceMaker
on Stack Overflow
See other posts from Stack Overflow
or by PeaceMaker
Published on 2012-10-23T05:29:03Z
Indexed on
2012/10/23
17:01 UTC
Read the original article
Hit count: 248
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 |
© Stack Overflow or respective owner