12.1. Predicates
Predicates are boolean functions that return true or false for a given set of input.
They are most commonly used to filter out subgraphs in the WHERE part of a query.
See also the section called “Comparison operators”.
Figure 12.1. Graph
ALL
Tests whether a predicate holds for all element of this collection collection.
Syntax: ALL(identifier in collection WHERE predicate)
Arguments:
- collection: An expression that returns a collection
- identifier: This is the identifier that can be used from the predicate.
- predicate: A predicate that is tested against all items in the collection.
Query.
MATCH p=(a)-[*1..3]->(b) WHERE a.name='Alice' AND b.name='Daniel' AND ALL (x IN nodes(p) WHERE x.age > 30) RETURN p
All nodes in the returned paths will have an age property of at least 30.
Result
| p |
|---|
| 1 row |
|
Try this query live. create (_0 {`age`:54, `eyes`:"brown", `name`:"Daniel"}) create (_1:`Spouse` {`age`:41, `array`:["one", "two", "three"], `eyes`:"blue", `name`:"Eskil"}) create (_2:`foo`:`bar` {`age`:38, `eyes`:"brown", `name`:"Alice"}) create (_3 {`age`:25, `eyes`:"blue", `name`:"Bob"}) create (_4 {`age`:53, `eyes`:"green", `name`:"Charlie"}) create _2-[:`KNOWS`]->_3 create _2-[:`KNOWS`]->_4 create _3-[:`KNOWS`]->_0 create _3-[:`MARRIED`]->_1 create _4-[:`KNOWS`]->_0 match p=(a)-[*1..3]->(b) where a.name='Alice' and b.name='Daniel' and all(x in nodes(p) WHERE x.age > 30) return p
ANY
Tests whether a predicate holds for at least one element in the collection.
Syntax: ANY(identifier in collection WHERE predicate)
Arguments:
- collection: An expression that returns a collection
- identifier: This is the identifier that can be used from the predicate.
- predicate: A predicate that is tested against all items in the collection.
Query.
MATCH (a) WHERE a.name='Eskil' AND ANY (x IN a.array WHERE x = "one") RETURN a
All nodes in the returned paths has at least one one value set in the array property named array.
Result
| a |
|---|
| 1 row |
|
Try this query live. create (_0 {`age`:54, `eyes`:"brown", `name`:"Daniel"}) create (_1:`Spouse` {`age`:41, `array`:["one", "two", "three"], `eyes`:"blue", `name`:"Eskil"}) create (_2:`foo`:`bar` {`age`:38, `eyes`:"brown", `name`:"Alice"}) create (_3 {`age`:25, `eyes`:"blue", `name`:"Bob"}) create (_4 {`age`:53, `eyes`:"green", `name`:"Charlie"}) create _2-[:`KNOWS`]->_3 create _2-[:`KNOWS`]->_4 create _3-[:`KNOWS`]->_0 create _3-[:`MARRIED`]->_1 create _4-[:`KNOWS`]->_0 match (a) where a.name='Eskil' and any(x in a.array WHERE x = "one") return a
NONE
Returns true if the predicate holds for no element in the collection.
Syntax: NONE(identifier in collection WHERE predicate)
Arguments:
- collection: An expression that returns a collection
- identifier: This is the identifier that can be used from the predicate.
- predicate: A predicate that is tested against all items in the collection.
Query.
MATCH p=(n)-[*1..3]->(b) WHERE n.name='Alice' AND NONE (x IN nodes(p) WHERE x.age = 25) RETURN p
No nodes in the returned paths has a age property set to 25.
Result
| p |
|---|
| 2 rows |
|
|
Try this query live. create (_0 {`age`:54, `eyes`:"brown", `name`:"Daniel"}) create (_1:`Spouse` {`age`:41, `array`:["one", "two", "three"], `eyes`:"blue", `name`:"Eskil"}) create (_2:`foo`:`bar` {`age`:38, `eyes`:"brown", `name`:"Alice"}) create (_3 {`age`:25, `eyes`:"blue", `name`:"Bob"}) create (_4 {`age`:53, `eyes`:"green", `name`:"Charlie"}) create _2-[:`KNOWS`]->_3 create _2-[:`KNOWS`]->_4 create _3-[:`KNOWS`]->_0 create _3-[:`MARRIED`]->_1 create _4-[:`KNOWS`]->_0 match p=(n)-[*1..3]->(b) where n.name='Alice' and NONE(x in nodes(p) WHERE x.age = 25) return p
SINGLE
Returns true if the predicate holds for exactly one of the elements in the collection.
Syntax: SINGLE(identifier in collection WHERE predicate)
Arguments:
- collection: An expression that returns a collection
- identifier: This is the identifier that can be used from the predicate.
- predicate: A predicate that is tested against all items in the collection.
Query.
MATCH p=(n)-->(b) WHERE n.name='Alice' AND SINGLE (var IN nodes(p) WHERE var.eyes = "blue") RETURN p
Exactly one node in every returned path will have the eyes property set to "blue".
Result
| p |
|---|
| 1 row |
|
Try this query live. create (_0 {`age`:54, `eyes`:"brown", `name`:"Daniel"}) create (_1:`Spouse` {`age`:41, `array`:["one", "two", "three"], `eyes`:"blue", `name`:"Eskil"}) create (_2:`foo`:`bar` {`age`:38, `eyes`:"brown", `name`:"Alice"}) create (_3 {`age`:25, `eyes`:"blue", `name`:"Bob"}) create (_4 {`age`:53, `eyes`:"green", `name`:"Charlie"}) create _2-[:`KNOWS`]->_3 create _2-[:`KNOWS`]->_4 create _3-[:`KNOWS`]->_0 create _3-[:`MARRIED`]->_1 create _4-[:`KNOWS`]->_0 match p=(n)-->(b) where n.name='Alice' and SINGLE(var in nodes(p) WHERE var.eyes = "blue") return p
EXISTS
Returns true if a match for the pattern exists in the graph, or the property exists in the node, relationship or map.
Syntax: EXISTS( pattern-or-property )
Arguments:
- pattern-or-property: A pattern or a property (in the form identifier.prop).
Query.
MATCH (n) WHERE EXISTS(n.name) RETURN n.name AS name, EXISTS((n)-[:MARRIED]->()) AS is_married
This query returns all the nodes with a name property along with a boolean true/false indicating if they are married.
Result
| name | is_married |
|---|---|
| 5 rows | |
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Try this query live. create (_0 {`age`:54, `eyes`:"brown", `name`:"Daniel"}) create (_1:`Spouse` {`age`:41, `array`:["one", "two", "three"], `eyes`:"blue", `name`:"Eskil"}) create (_2:`foo`:`bar` {`age`:38, `eyes`:"brown", `name`:"Alice"}) create (_3 {`age`:25, `eyes`:"blue", `name`:"Bob"}) create (_4 {`age`:53, `eyes`:"green", `name`:"Charlie"}) create _2-[:`KNOWS`]->_3 create _2-[:`KNOWS`]->_4 create _3-[:`KNOWS`]->_0 create _3-[:`MARRIED`]->_1 create _4-[:`KNOWS`]->_0 match (n) where EXISTS(n.name) return n.name AS name, EXISTS( (n)-[:MARRIED]->() ) AS is_married