Is it possible to create a variable and make its assignment based on certain conditions in a cypher query?

Question

I am trying to create an array of values that will be assigned based on the outcome of a case test. This test will be inside a query that I already know works with a preset value in the query.

The query I am trying to embed in the case test is something like this:

WITH SPLIT (('07/28/2015'), '/' AS cd
MATCH (nodeA: NodeTypeA)-(r:ARelation)->(nodeB: NodeTypeB)
WITH cd, SPLIT (nodeA.ADate, '/') AS dd, nodeA, nodeB, r
WHERE
    (TOINT(cd[2])> TOINT(dd[2])) OR (TOINT(cd[2]= TOINT(dd[2]) AND ((TOINT(cd[0])> TOINT(dd[0])) OR (TOINT(cd[0])= TOINT(dd[0]) AND (TOINT(cd[1])>= TOINT(dd[1])))))
RETURN nodeA, nodeB, r

I want to replace the current date with whatever date will be 6 months from the current date, and I came up with something like this, though I am not sure where I would put it in my query or if it would even work (do I initialize the new variable for instance somehow?):

WHEN ((TOINT(cd[0])> 6))
THEN 
  TOINT(fd[2])=TOINT(cd[2])+1, TOINT(fd[0])=TOINT(cd[0])-6, TOINT(fd[1])=TOINT(cd[1])
ELSE
  TOINT(fd[2])=TOINT(cd[2]), TOINT(fd[0])=TOINT(cd[0])+6, TOINT(fd[1])=TOINT(cd[1])

fd would then replace the cd in the original query's WHERE segment. Where would my case test go, is it correctly written (and if not, what is wrong), and would I need something else added to make it all work?

Answer 1

Just use a WITH block to do a computation and bind it to a new variable, like this:

WITH 2 + 2 as y RETURN y;

That basically assigns the value 4 to y.

In your query, you already have a big WITH block. Just put your computations in those, bound to new variables, and you can then refer to those variables in subsequent expressions.

Don't try to modify these variables, just create new ones (with new WITH blocks) as needed. If you need variables that can actually change, then...well hey you're working with a database, the ultimate way to store and update information. Create a new node, and then update it as you see fit. :)

Answer 2

This is my proposed solution Explanation: I have declared four variables in my query i.e. name1, name2, ken and lana and I am using these variables for creating MATCH pattern (in the MATCH clause) and filtering those in the Where clause.

WITH    "Lau" AS name1,
        "L" AS name2,
        "Keanu Reeves" AS ken,
        "Lana Wachowski" AS lana
MATCH(x:Person{ name: ken})-[:ACTED_IN]->(m:Movie)<-[:ACTED_IN]-(y:Person),
        (x1:Person{name: lana})-[:DIRECTED]->(m)<-[:DIRECTED]-(y1:Person)

WHERE y.name CONTAINS name1 OR
      y.name CONTAINS name2 OR
      (y.name CONTAINS name1 AND y.name CONTAINS name2)
RETURN x, m, y, x1;