SET and REMOVE node attributes in one statement

Neo4j Graph Platform Cypher
1

I am now into my second hour of experimenting with Neo4J. Thus far, I am very very impressed with what I see. The tutorials, the Windows desktop version, the syntax of Cypher... are pretty much perfect. However, I am finding it difficult to understand just how I should make multiple changes to a node in one statement.

For the present purpose I am simply working with the default Movies database. Suppose I want to do the following

  1. Create a Person with an additional role of "Alien"
  2. Give that instance of Person the additional attribute of Peau = 'Green'
  3. Change my mind and decide that the attribute name/value pair should be in English rather than French
  4. So at this stage I want to REMOVE peau and SET skin.

Not a problem in itself if I use the following sequence

CREATE (p:Person:Alien {name:'ET'});
MATCH(a:Alien) RETURN a;
//all good Person with the extra role of fAlien now exists
MATCH(a:Alien) SET a.born = 1987 RETURN s;
//still good
MATCH(a:Alien) SET a.peau = 'Verte' RETURN a;
//our Alien now has a green skin - in French
MATCH(a:Alien) SET a.skin = 'Green' RETURN a;
//our Alien now also has a green skin in English
MATCH(a:Alien) REMOVE a.peau RETURN a;
//all good, stripped out that unrequired French peau attribute

While this works it does seem like unnecessary extra work.  Surely, I should be able to SET and REMOVE in one statement.  However,

MATCH(a:Alien)  SET a.skin = 'Green' REMOVE a.peau = 'Verte' RETURN a;

Yes, that worked too. However, with my pgSQL background this feels a bit odd to me. Put in a comma before the REMOVE and Cypher throws up an error because it does not understand - it thinks I am attempting to continue the prior SET... . Is the way I have written the statement the only valid way to accomplish what I need here?

2

You can do it all in one statement, like this:

CREATE (a:Person:Alien {name:'ET'})

//all good Person with the extra role of fAlien now exists
SET a.born = 1987
//still good
SET a.peau = 'Verte'
//our Alien now has a green skin - in French
SET a.skin = 'Green'
//our Alien now also has a green skin in English
REMOVE a.peau RETURN a;
//all good, stripped out that unrequired French peau attribute

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3

Thanks. To put my question another way - when does one use commas in Cypher. From my understanding thus far only to separate node attributes/properties. When issuing Cypher commands - e.g. SET, DELETE etc - you do not. Presumably the freshly issued command, e.g, DELETE, "closes the previous command, e.g. SET.

Is my understanding correct?

4

You can use the commas when you're creating stuff. e.g.

CREATE (:Person {id: 1}), (:Person {id: 2})

And then you can also use them when you're trying to find things:

MATCH (p1:Person {id: 1}), (p2:Person {id: 2})

On and also if you wanted to set multiple properties:

MATCH (p1:Person {id: 1})
SET p1.time = time(), p1.date = date()
RETURN p1

And then the ; ends a statement.