linear combination of multiple properties

[gg4u]

Hi folks!

so, today I was experimenting on obtaining a linear combination out of multiple types of properties.

Suppose you have multiple REL types, each with weighted properties.

I am trying to obtain a collection? of first neighbors to a node, ordered by the sum of two weights.

Here's what i've done:

MATCH (n:TYPE)

WHERE n.id = 'hellyeah'

OPTIONAL MATCH n-[r:P]-m

OPTIONAL MATCH n-[s:P2]-m

RETURN n,r,s,m

with this query, i get a table BUT all values of s are set as

NULL 

could you help me understand 

why?

thank you!

[gg4u]

Another simple attempt is to obtain different type of rel (r,s) going from a node to others (n-m).

I tried:

MATCH (n:TYPE)-[s:P1]-m

WHERE n.id = 'myname'

WITH n,s,m

MATCH m-[r:P2]-n

RETURN r,s

but it returns 0 rows,

Both the two matches from the node n.id, return not empty results in a single query (one match per query).

Why do r, s return no results with the combined query ?

[Michael Hunger]

That's probably because you'd want to use two different _m's_ otherwise the first m is reused for the second match.

MATCH (n:TYPE)

WHERE n.id = 'hellyeah'

OPTIONAL MATCH (n)-[r:P]-(m1)

OPTIONAL MATCH (n)-[s:P2]-(m2)

RETURN n,r,s,m1,m2

You can also optimize this a bit to do the second bit of matches not for each of the first

Something like this:

MATCH (n:TYPE)

WHERE n.id = 'hellyeah'

OPTIONAL MATCH (n)-[r:P]-(m1)

WITH n, collect({rel:r, node:m1}) as neighbours

OPTIONAL MATCH (n)-[s:P2]-(m2)

WITH collect({rel:s, node:m2}) + neighbours as neighbours

UNWIND neighbours  as nb

RETURN nb

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[XDiscovery Team]

mmm thank you Michael,

i will try this out.

i was also getting 0 rows because i noticed that i previously created relationshpis between nodes by limiting the results, so it was not said that, between two nodes, there would have been the two types of relationships I was looking for.

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