# Check if node exists and use the result as a condition **URL:** \ **Category:** Cypher\ **Created:** [January 14, 2021, 6:14pm UTC](https://community.neo4j.com/t/check-if-node-exists-and-use-the-result-as-a-condition/32069 "2021-01-14T18:14:13Z")\ **Posts on this page:** 15\ **Page:** 1
**Author:** ![janezic](https://sea1.discourse-cdn.com/flex021/user_avatar/community.neo4j.com/janezic/32/6712_2.png) [@janezic](https://community.neo4j.com/u/janezic)\ **Post date:** [January 14, 2021, 6:14pm UTC](https://community.neo4j.com/t/check-if-node-exists-and-use-the-result-as-a-condition/32069/1 "2021-01-14T18:14:13Z")
Sorry, to ask this question for the 100th time, but none of the previous posts was similar to my problem: I just want to get back TRUE or FALSE if a node with a certain label and a certain value of a property exists. (u:User {user\_id: 1} =\> TRUE / FALSE All other posts where about MERGE and so on, but I don't want to create anything, I want to use it as a condition in an apoc.do.when-function. ---
**Author:** ![clem](https://sea1.discourse-cdn.com/flex021/user_avatar/community.neo4j.com/clem/32/4364_2.png) [@clem](https://community.neo4j.com/u/clem)\ **Post date:** [January 14, 2021, 7:32pm UTC](https://community.neo4j.com/t/check-if-node-exists-and-use-the-result-as-a-condition/32069/2 "2021-01-14T19:32:10Z")
This is tricky! the` exists()` function doesn't work the way I had hoped... and you can't compare the `MATCH` results with `null`. but this works: ```auto MATCH (u:User {user_id: 1}) WITH count(*) as count CALL apoc.when (count > 0, // won't work so well if user_id isn't unique... "RETURN true AS bool", // one or more users with user_id = 1 "RETURN false AS bool", // no users with user_id = 1 {count:count} ) YIELD value return value.bool ``` There may be a better way to do this, but I don't know.. Remember `apoc.do.when` is for when you want to change the DB, `apoc.when` is if you are just reading. [added] a better solution is further towards the end of this thread! ---
**Author:** ![janezic](https://sea1.discourse-cdn.com/flex021/user_avatar/community.neo4j.com/janezic/32/6712_2.png) [@janezic](https://community.neo4j.com/u/janezic)\ **Post date:** [January 14, 2021, 8:56pm UTC](https://community.neo4j.com/t/check-if-node-exists-and-use-the-result-as-a-condition/32069/3 "2021-01-14T20:56:32Z")
Thanks a lot, I have tried it with exists() and comparing with NULL - and as you said without any success. I did not come to the conclusion to try it with count(). I basically don't understand why Cypher (or at least APOC) does not provide a function for that. ---
**Author:** ![clem](https://sea1.discourse-cdn.com/flex021/user_avatar/community.neo4j.com/clem/32/4364_2.png) [@clem](https://community.neo4j.com/u/clem)\ **Post date:** [January 14, 2021, 9:09pm UTC](https://community.neo4j.com/t/check-if-node-exists-and-use-the-result-as-a-condition/32069/4 "2021-01-14T21:09:59Z")
I don't know either... The Cypher language could evolve to do this, but it's still a relatively young language, so maybe it will get extended. ---
**Author:** ![dominicvivek06](https://sea1.discourse-cdn.com/flex021/user_avatar/community.neo4j.com/dominicvivek06/32/5034_2.png) [@dominicvivek06](https://community.neo4j.com/u/dominicvivek06)\ **Post date:** [January 15, 2021, 12:32am UTC](https://community.neo4j.com/t/check-if-node-exists-and-use-the-result-as-a-condition/32069/5 "2021-01-15T00:32:56Z")
Hi @janezic , hope this works ... try this CASE expression > **[Expressions - Cypher Manual](https://neo4j.com/docs/cypher-manual/current/syntax/expressions/)** > > This section contains an overview of expressions in Cypher with examples. ```auto merge (p:Person{name:"Dominic",db:"Neo4j"}); Added 1 label, created 1 node, set 2 properties, completed after 6 ms. merge (p:Person{name:"Kumar"}); Added 1 label, created 1 node, set 1 property, completed after 6 ms. match (n) return (n) ╒═══════════════════════════════╕ │"n" │ ╞═══════════════════════════════╡ │{"name":"Dominic","db":"Neo4j"}│ ├───────────────────────────────┤ │{"name":"Kumar"} │ └───────────────────────────────┘ MATCH (p:Person) RETURN p.name, CASE WHEN exists(p.db) THEN true ELSE false END AS db_property_status; ╒═════════╤════════════════════╕ │"p.name" │"db_property_status"│ ╞═════════╪════════════════════╡ │"Dominic"│true │ ├─────────┼────────────────────┤ │"Kumar" │false │ └─────────┴────────────────────┘ ``` ---
**Author:** ![clem](https://sea1.discourse-cdn.com/flex021/user_avatar/community.neo4j.com/clem/32/4364_2.png) [@clem](https://community.neo4j.com/u/clem)\ **Post date:** [January 15, 2021, 1:03am UTC](https://community.neo4j.com/t/check-if-node-exists-and-use-the-result-as-a-condition/32069/6 "2021-01-15T01:03:18Z")
Sorry, this solves _ **different question** _: whether a **property exists** , not whether a **node** with a specific value exists. ---
**Author:** ![dominicvivek06](https://sea1.discourse-cdn.com/flex021/user_avatar/community.neo4j.com/dominicvivek06/32/5034_2.png) [@dominicvivek06](https://community.neo4j.com/u/dominicvivek06)\ **Post date:** [January 15, 2021, 1:11am UTC](https://community.neo4j.com/t/check-if-node-exists-and-use-the-result-as-a-condition/32069/7 "2021-01-15T01:11:05Z")
@clem , please, visit the CASE statement documentation -\> [Expressions - Cypher Manual](https://neo4j.com/docs/cypher-manual/current/syntax/expressions/#syntax-simple-case). It can be simply changed to condition. CASE statements exists from RDBMS too. @janezic ```auto match (n) return (n) ╒═══════════════════════════════╕ │"n" │ ╞═══════════════════════════════╡ │{"name":"Dominic","db":"Neo4j"}│ ├───────────────────────────────┤ │{"name":"Kumar"} │ └───────────────────────────────┘ MATCH (p:Person) RETURN p.name, CASE WHEN p.db="Neo4j" THEN true ELSE false END AS db_property_status; ╒═════════╤════════════════════╕ │"p.name" │"db_property_status"│ ╞═════════╪════════════════════╡ │"Dominic"│true │ ├─────────┼────────────────────┤ │"Kumar" │false │ └─────────┴────────────────────┘ ``` ---
**Author:** ![janezic](https://sea1.discourse-cdn.com/flex021/user_avatar/community.neo4j.com/janezic/32/6712_2.png) [@janezic](https://community.neo4j.com/u/janezic)\ **Post date:** [January 15, 2021, 7:34am UTC](https://community.neo4j.com/t/check-if-node-exists-and-use-the-result-as-a-condition/32069/8 "2021-01-15T07:34:46Z")
Good Morning, thank you, but no, this is basically not exactly what I was looking for, because it gives me **all** users with all their email-addresses with a additional column true/false. Of course you could filter it again, but this is a very expensive query. I just want to know, if a node with a certain value of a property exists. ---
**Author:** ![tard\_gabriel](https://sea1.discourse-cdn.com/flex021/user_avatar/community.neo4j.com/tard_gabriel/32/28033_2.png) [@tard\_gabriel](https://community.neo4j.com/u/tard_gabriel)\ **Post date:** [January 15, 2021, 7:48am UTC](https://community.neo4j.com/t/check-if-node-exists-and-use-the-result-as-a-condition/32069/9 "2021-01-15T07:48:59Z")
> [@janezic](#): > > I just want to get back TRUE or FALSE if a node with a certain label and a certain value of a property exists. Wow, at the beginning I was pfff that's super easy...hoo no that's not indeed. Funny, I like challenge, I didn't solve it yet but I see a OPTIONAL MATCH clause as an work around solution. And by the way, null laws of neo4j implies that null is not equal to null since null is nothing not a value and then since we don't know what it is you can't compare something you don't know with something you don't know. ---
**Author:** ![tard\_gabriel](https://sea1.discourse-cdn.com/flex021/user_avatar/community.neo4j.com/tard_gabriel/32/28033_2.png) [@tard\_gabriel](https://community.neo4j.com/u/tard_gabriel)\ **Post date:** [January 15, 2021, 8:03am UTC](https://community.neo4j.com/t/check-if-node-exists-and-use-the-result-as-a-condition/32069/10 "2021-01-15T08:03:28Z")
OPTIONAL MATCH (n:Label {property:value}) RETURN exists(n.property) AS Predicate It will give you one row with true or null as output, it's not exactly the end result wanted but it's the closer one I got for now. ---
**Author:** ![clem](https://sea1.discourse-cdn.com/flex021/user_avatar/community.neo4j.com/clem/32/4364_2.png) [@clem](https://community.neo4j.com/u/clem)\ **Post date:** [January 15, 2021, 8:09am UTC](https://community.neo4j.com/t/check-if-node-exists-and-use-the-result-as-a-condition/32069/11 "2021-01-15T08:09:37Z")
If you add `IS NOT null` then you will get a true when property has the value /false when the property doesn't have the value. I hadn't thought of using `OPTIONAL`. Clever! Also you don't need `exists()`; you can just test `n` for `null` ```auto OPTIONAL MATCH (n:User{user_id:1}) RETURN n IS NOT NULL AS Predicate ``` (note `exists(n)` doesn't work.) This is a good example of using `OPTIONAL`. [added] Without `OPTIONAL` and if User with user\_id = 1 doesn't exist, then the `MATCH` returns _ **no records** _ which is different than returning `null`. Subtle! Also reminder for Cypher beginners: the test `n <> null` is incorrect for testing null/non-null. This is correct: `n IS NOT null` ---
**Author:** ![janezic](https://sea1.discourse-cdn.com/flex021/user_avatar/community.neo4j.com/janezic/32/6712_2.png) [@janezic](https://community.neo4j.com/u/janezic)\ **Post date:** [January 15, 2021, 8:14am UTC](https://community.neo4j.com/t/check-if-node-exists-and-use-the-result-as-a-condition/32069/12 "2021-01-15T08:14:37Z")
Wow, the solution is so simple and so hard to find on the other hand. THANK YOU!!! ---
**Author:** ![tard\_gabriel](https://sea1.discourse-cdn.com/flex021/user_avatar/community.neo4j.com/tard_gabriel/32/28033_2.png) [@tard\_gabriel](https://community.neo4j.com/u/tard_gabriel)\ **Post date:** [January 15, 2021, 8:19am UTC](https://community.neo4j.com/t/check-if-node-exists-and-use-the-result-as-a-condition/32069/13 "2021-01-15T08:19:20Z")
The key here is this fact: MATCH return nothing if he finds nothing OPTIONAL MATCH always return at least null Thanks clem I was looking for an operator for the null or something like that. I didn't know you could use a lonely optional match 🤔 We did it, next challenge. ---
**Author:** ![clem](https://sea1.discourse-cdn.com/flex021/user_avatar/community.neo4j.com/clem/32/4364_2.png) [@clem](https://community.neo4j.com/u/clem)\ **Post date:** [January 15, 2021, 8:23am UTC](https://community.neo4j.com/t/check-if-node-exists-and-use-the-result-as-a-condition/32069/14 "2021-01-15T08:23:51Z")
I added a suggestion to the documentation for `OPTIONAL MATCH`. This is a great example! I've learned a lot! Thanks for showing us `OPTIONAL MATCH`. I hadn't quite appreciated what it could do. ---
**Author:** ![astrosam](https://sea1.discourse-cdn.com/flex021/user_avatar/community.neo4j.com/astrosam/32/26153_2.png) [@astrosam](https://community.neo4j.com/u/astrosam)\ **Post date:** [July 14, 2023, 2:48am UTC](https://community.neo4j.com/t/check-if-node-exists-and-use-the-result-as-a-condition/32069/15 "2023-07-14T02:48:24Z")
I just found this thread. I have some comments about the proposed solution: ```auto OPTIONAL MATCH (n:User{user_id:1}) RETURN n IS NOT NULL AS Predicate ``` The above solution is not appropriate if the OPTIONAL MATCH can find multiple (N) matches. That is because in that case it would: (1) do the work to find all N matches and not stop after finding just the first one, and (2) it would return N Predicate values (all true). Here is one simple way to fix both issues: ```auto OPTIONAL MATCH (n:User{user_id:1}) WITH n LIMIT 1 RETURN n IS NOT NULL AS Predicate ``` There are other solutions as well, including using the EXISTS() function properly. The EXISTS function must be passed a pattern _that has a relationship_. Here is a tricky way to use a 0-length variable relationship pattern with EXISTS to match a node (that does not need to have a relationship). It is, unfortunately, hard to read; but it does work. ```auto RETURN EXISTS((:User{user_id:1})-[*0]-()) AS Predicate ``` Also, neo4j 5.3 added the [EXISTS subquery](https://neo4j.com/docs/cypher-manual/current/syntax/expressions/#existential-subqueries), which is a little easier to read: ```auto RETURN EXISTS { (:User{user_id:1}) } AS Predicate ```