Cypher is the declarative query language for Neo4j, the world’s leading graph database.
Key principles and capabilities of Cypher are as follows:
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Cypher matches patterns of nodes and relationship in the graph, to extract information or modify the data.
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Cypher has the concept of identifiers which denote named, bound elements and parameters.
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Cypher can create, update, and remove nodes, relationships, labels, and properties.
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Cypher manages indexes and constraints.
You can try Cypher snippets live in the Neo4j Console at console.neo4j.org or read the full Cypher documentation in the Neo4j Developer Manual. For live graph models using Cypher check out GraphGist.
The Cypher Refcard is also available in PDF format.
Note: {value} denotes either literals, for ad hoc Cypher queries; or parameters, which is the best practice for applications. Neo4j properties can be strings, numbers, booleans or arrays thereof. Cypher also supports maps and lists.
Syntax
Read Query Structure |
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[MATCH WHERE] [OPTIONAL MATCH WHERE] [WITH [ORDER BY] [SKIP] [LIMIT]] RETURN [ORDER BY] [SKIP] [LIMIT] |
MATCH |
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MATCH (n:Person)-[:KNOWS]->(m:Person) WHERE n.name = "Alice" Node patterns can contain labels and properties. |
MATCH (n)-->(m) Any pattern can be used in MATCH. |
MATCH (n {name: "Alice"})-->(m) Patterns with node properties. |
MATCH p = (n)-->(m) Assign a path to p. |
OPTIONAL MATCH (n)-[r]->(m) Optional pattern, NULLs will be used for missing parts. |
WHERE m.name = "Alice" Force the planner to use a label scan to solve the query (for manual performance tuning). |
WHERE |
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WHERE n.property <> {value} Use a predicate to filter. Note that WHERE is always part of a MATCH, OPTIONAL MATCH, WITH or START clause. Putting it after a different clause in a query will alter what it does. |
RETURN |
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RETURN * Return the value of all variables. |
RETURN n AS columnName Use alias for result column name. |
RETURN DISTINCT n Return unique rows. |
ORDER BY n.property Sort the result. |
ORDER BY n.property DESC Sort the result in descending order. |
SKIP {skipNumber} Skip a number of results. |
LIMIT {limitNumber} Limit the number of results. |
SKIP {skipNumber} LIMIT {limitNumber} Skip results at the top and limit the number of results. |
RETURN count(*) The number of matching rows. See Aggregation for more. |
WITH |
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MATCH (user)-[:FRIEND]-(friend) WHERE user.name = {name} WITH user, count(friend) AS friends WHERE friends > 10 RETURN user The WITH syntax is similar to RETURN. It separates query parts explicitly, allowing you to declare which variables to carry over to the next part. |
MATCH (user)-[:FRIEND]-(friend) WITH user, count(friend) AS friends ORDER BY friends DESC SKIP 1 LIMIT 3 RETURN user You can also use ORDER BY, SKIP, LIMIT with WITH. |
UNION |
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MATCH (a)-[:KNOWS]->(b) RETURN b.name UNION MATCH (a)-[:LOVES]->(b) RETURN b.name Returns the distinct union of all query results. Result column types and names have to match. |
MATCH (a)-[:KNOWS]->(b) RETURN b.name UNION ALL MATCH (a)-[:LOVES]->(b) RETURN b.name Returns the union of all query results, including duplicated rows. |
Write-Only Query Structure |
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(CREATE [UNIQUE] | MERGE)* [SET|DELETE|REMOVE|FOREACH]* [RETURN [ORDER BY] [SKIP] [LIMIT]] |
Read-Write Query Structure |
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[MATCH WHERE] [OPTIONAL MATCH WHERE] [WITH [ORDER BY] [SKIP] [LIMIT]] (CREATE [UNIQUE] | MERGE)* [SET|DELETE|REMOVE|FOREACH]* [RETURN [ORDER BY] [SKIP] [LIMIT]] |
CREATE |
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CREATE (n {name: {value}}) Create a node with the given properties. |
CREATE (n {map}) Create a node with the given properties. |
UNWIND {listOfMaps} AS properties CREATE (n) SET n = properties Create nodes with the given properties. |
CREATE (n)-[r:KNOWS]->(m) Create a relationship with the given type and direction; bind a variable to it. |
CREATE (n)-[:LOVES {since: {value}}]->(m) Create a relationship with the given type, direction, and properties. |
MERGE |
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MERGE (n:Person {name: {value}}) ON CREATE SET n.created = timestamp() ON MATCH SET n.counter = coalesce(n.counter, 0) + 1, n.accessTime = timestamp() Match pattern or create it if it does not exist. Use ON CREATE and ON MATCH for conditional updates. |
MATCH (a:Person {name: {value1}}), (b:Person {name: {value2}}) MERGE (a)-[r:LOVES]->(b) MERGE finds or creates a relationship between the nodes. |
MATCH (a:Person {name: {value1}}) MERGE (a)-[r:KNOWS]->(b:Person {name: {value3}}) MERGE finds or creates subgraphs attached to the node. |
SET |
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SET n.property1 = {value1}, n.property2 = {value2} Update or create a property. |
SET n = {map} Set all properties. This will remove any existing properties. |
SET n += {map} Add and update properties, while keeping existing ones. |
SET n:Person Adds a label Person to a node. |
DELETE |
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DELETE n, r Delete a node and a relationship. |
DETACH DELETE n Delete a node and all relationships connected to it. |
MATCH (n) DETACH DELETE n Delete all nodes and relationships from the database. |
REMOVE |
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REMOVE n:Person Remove a label from n. |
REMOVE n.property Remove a property. |
FOREACH |
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FOREACH (r IN rels(path) | SET r.marked = TRUE) Execute a mutating operation for each relationship of a path. |
FOREACH (value IN coll | CREATE (:Person {name: value})) Execute a mutating operation for each element in a list. |
CALL |
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CALL db.labels() YIELD label This shows a standalone call to the built-in procedure db.labels to list all labels used in the database. Note that required procedure arguments are given explicitly in brackets after the procedure name. |
CALL java.stored.procedureWithArgs Standalone calls may omit YIELD and also provide arguments implicitly via statement parameters, e.g. a standalone call requiring one argument input may be run by passing the parameter map {input: 'foo'}. |
CALL db.labels() YIELD label RETURN count(label) AS count Calls the built-in procedure db.labels inside a larger query to count all labels used in the database. Calls inside a larger query always requires passing arguments and naming results explicitly with YIELD. |
INDEX |
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CREATE INDEX ON :Person(name) Create an index on the label Person and property name. |
MATCH (n:Person) WHERE n.name = {value} An index can be automatically used for the equality comparison. Note that for example lower(n.name) = {value} will not use an index. |
MATCH (n:Person) WHERE n.name IN [{value}] An index can be automatically used for the IN list checks. |
MATCH (n:Person) USING INDEX n:Person(name) WHERE n.name = {value} Index usage can be enforced, when Cypher uses a suboptimal index or more than one index should be used. |
DROP INDEX ON :Person(name) Drop the index on the label Person and property name. |
CONSTRAINT |
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CREATE CONSTRAINT ON (p:Person) ASSERT p.name IS UNIQUE Create a unique property constraint on the label Person and property name. If any other node with that label is updated or created with a name that already exists, the write operation will fail. This constraint will create an accompanying index. |
DROP CONSTRAINT ON (p:Person) ASSERT p.name IS UNIQUE Drop the unique constraint and index on the label Person and property name. |
CREATE CONSTRAINT ON (p:Person) ASSERT exists(p.name) Create a node property existence constraint on the label Person and property name. If a node with that label is created without a name, or if the name property is removed from an existing node with the Person label, the write operation will fail. |
DROP CONSTRAINT ON (p:Person) ASSERT exists(p.name) Drop the node property existence constraint on the label Person and property name. |
CREATE CONSTRAINT ON ()-[l:LIKED]-() ASSERT exists(l.when) Create a relationship property existence constraint on the type LIKED and property when. If a relationship with that type is created without a when, or if the when property is removed from an existing relationship with the LIKED type, the write operation will fail. |
DROP CONSTRAINT ON ()-[l:LIKED]-() ASSERT exists(l.when) Drop the relationship property existence constraint on the type LIKED and property when. |
Import |
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LOAD CSV FROM 'http://neo4j.com/docs/3.0.6/cypher-refcard/csv/artists.csv' AS line CREATE (:Artist {name: line[1], year: toInt(line[2])}) Load data from a CSV file and create nodes. |
LOAD CSV WITH HEADERS FROM 'http://neo4j.com/docs/3.0.6/cypher-refcard/csv/artists-with-headers.csv' AS line CREATE (:Artist {name: line.Name, year: toInt(line.Year)}) Load CSV data which has headers. |
LOAD CSV FROM 'http://neo4j.com/docs/3.0.6/cypher-refcard/csv/artists-fieldterminator.csv' AS line FIELDTERMINATOR ';' CREATE (:Artist {name: line[1], year: toInt(line[2])}) Use a different field terminator, not the default which is a comma (with no whitespace around it). |
Operators | |
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Mathematical |
+, -, *, /, %, ^ |
Comparison |
=, <>, <, >, <=, >= |
Boolean |
AND, OR, XOR, NOT |
String |
+ |
List |
+, IN, [x], [x .. y] |
Regular Expression |
=~ |
String matching |
STARTS WITH, ENDS WITH, CONTAINS |
NULL |
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Patterns |
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(n:Person) Node with Person label. |
(n:Person:Swedish) Node with both Person and Swedish labels. |
(n:Person {name: {value}}) Node with the declared properties. |
(n)-->(m) Relationship from n to m. |
(n)--(m) Relationship in any direction between n and m. |
(n:Person)-->(m) Node n labeled Person with relationship to m. |
(m)<-[:KNOWS]-(n) Relationship of type KNOWS from n to m. |
(n)-[:KNOWS|:LOVES]->(m) Relationship of type KNOWS or of type LOVES from n to m. |
(n)-[r]->(m) Bind the relationship to variable r. |
(n)-[*1..5]->(m) Variable length path of between 1 and 5 relationships from n to m. |
(n)-[*]->(m) Variable length path of any number of relationships from n to m. (Please see the performance tips.) |
(n)-[:KNOWS]->(m {property: {value}}) A relationship of type KNOWS from a node n to a node m with the declared property. |
shortestPath((n1:Person)-[*..6]-(n2:Person)) Find a single shortest path. |
allShortestPaths((n1:Person)-[*..6]->(n2:Person)) Find all shortest paths. |
size((n)-->()-->()) Count the paths matching the pattern. |
Labels |
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CREATE (n:Person {name: {value}}) Create a node with label and property. |
MERGE (n:Person {name: {value}}) Matches or creates unique node(s) with label and property. |
SET n:Spouse:Parent:Employee Add label(s) to a node. |
MATCH (n:Person) Matches nodes labeled Person. |
MATCH (n:Person) WHERE n.name = {value} Matches nodes labeled Person with the given name. |
WHERE (n:Person) Checks existence of label on node. |
labels(n) Labels of the node. |
REMOVE n:Person Remove label from node. |
Lists |
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["a", "b", "c"] AS coll Literal lists are declared in square brackets. |
size({coll}) AS len, {coll}[0] AS value Lists can be passed in as parameters. |
range({firstNum}, {lastNum}, {step}) AS coll Range creates a list of numbers (step is optional), other functions returning list are: labels, nodes, relationships, rels, filter, extract. |
MATCH (a)-[r:KNOWS*]->() RETURN r AS rels Relationship variables of a variable length path contain a list of relationships. |
RETURN matchedNode.coll[0] AS value, size(matchedNode.coll) AS len Properties can be lists of strings, numbers or booleans. |
coll[{idx}] AS value, coll[{startIdx}..{endIdx}] AS slice List elements can be accessed with idx subscripts in square brackets. Invalid indexes return NULL. Slices can be retrieved with intervals from start_idx to end_idx each of which can be omitted or negative. Out of range elements are ignored. |
UNWIND {names} AS name MATCH (n {name: name}) RETURN avg(n.age) With UNWIND, you can transform any list back into individual rows. The example matches all names from a list of names. |
Maps |
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{name: "Alice", age: 38, address: {city: "London", residential: true}} Literal maps are declared in curly braces much like property maps. Nested maps and list are supported. |
MERGE (p:Person {name: {map}.name}) ON CREATE SET p = {map} Maps can be passed in as parameters and used as map or by accessing keys. |
MATCH (matchedNode:Person) RETURN matchedNode Nodes and relationships are returned as maps of their data. |
map.name, map.age, map.children[0] Map entries can be accessed by their keys. Invalid keys result in an error. |
Relationship Functions |
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type(a_relationship) String representation of the relationship type. |
startNode(a_relationship) Start node of the relationship. |
endNode(a_relationship) End node of the relationship. |
id(a_relationship) The internal id of the relationship. |
Predicates |
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n.property <> {value} Use comparison operators. |
exists(n.property) Use functions. |
n.number >= 1 AND n.number <= 10 Use boolean operators to combine predicates. |
1 <= n.number <= 10 Use chained operators to combine predicates. |
n:Person Check for node labels. |
variable IS NULL Check if something is NULL. |
NOT exists(n.property) OR n.property = {value} Either property does not exist or predicate is TRUE. |
n.property = {value} Non-existing property returns NULL, which is not equal to anything. |
n["property"] = {value} Properties may also be accessed using a dynamically computed property name. |
n.property STARTS WITH "Tob" OR n.property ENDS WITH "n" OR n.property CONTAINS "goodie" String matching. |
n.property =~ "Tob.*" String regular expression matching. |
(n)-[:KNOWS]->(m) Make sure the pattern has at least one match. |
NOT (n)-[:KNOWS]->(m) Exclude matches to (n)-[:KNOWS]->(m) from the result. |
n.property IN [{value1}, {value2}] Check if an element exists in a list. |
List Predicates |
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all(x IN coll WHERE exists(x.property)) Returns true if the predicate is true for all elements of the list. |
any(x IN coll WHERE exists(x.property)) Returns true if the predicate is true for at least one element of the list. |
none(x IN coll WHERE exists(x.property)) Returns true if the predicate is false for all elements of the list. |
single(x IN coll WHERE exists(x.property)) Returns true if the predicate is true for exactly one element in the list. |
Functions |
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coalesce(n.property, {defaultValue}) The first non-NULL expression. |
timestamp() Milliseconds since midnight, January 1, 1970 UTC. |
id(nodeOrRelationship) The internal id of the relationship or node. |
toInt({expr}) Converts the given input into an integer if possible; otherwise it returns NULL. |
toFloat({expr}) Converts the given input into a floating point number if possible; otherwise it returns NULL. |
keys({expr}) Returns a list of string representations for the property names of a node, relationship, or map. |
Path Functions |
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length(path) The number of relationships in the path. |
nodes(path) The nodes in the path as a list. |
relationships(path) The relationships in the path as a list. |
extract(x IN nodes(path) | x.prop) Extract properties from the nodes in a path. |
List Expressions |
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size({coll}) Number of elements in the list. |
head({coll}), last({coll}), tail({coll}) head returns the first, last the last element of the list. tail returns all but the first element. All return NULL for an empty list. |
[x IN coll WHERE x.prop <> {value} | x.prop] Combination of filter and extract in a concise notation. |
extract(x IN coll | x.prop) A list of the value of the expression for each element in the original list. |
filter(x IN coll WHERE x.prop <> {value}) A filtered list of the elements where the predicate is TRUE. |
reduce(s = "", x IN coll | s + x.prop) Evaluate expression for each element in the list, accumulate the results. |
Mathematical Functions |
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abs({expr}) The absolute value. |
rand() Returns a random number in the range from 0 (inclusive) to 1 (exclusive), [0,1). Returns a new value for each call. Also useful for selecting subset or random ordering. |
round({expr}) Round to the nearest integer, ceil and floor find the next integer up or down. |
sqrt({expr}) The square root. |
sign({expr}) 0 if zero, -1 if negative, 1 if positive. |
sin({expr}) Trigonometric functions, also cos, tan, cot, asin, acos, atan, atan2, haversin. All arguments for the trigonometric functions should be in radians, if not otherwise specified. |
degrees({expr}), radians({expr}), pi() Converts radians into degrees, use radians for the reverse. pi for π. |
log10({expr}), log({expr}), exp({expr}), e() Logarithm base 10, natural logarithm, e to the power of the parameter. Value of e. |
String Functions |
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toString({expression}) String representation of the expression. |
replace({original}, {search}, {replacement}) Replace all occurrences of search with replacement. All arguments are be expressions. |
substring({original}, {begin}, {subLength}) Get part of a string. The subLength argument is optional. |
left({original}, {subLength}), right({original}, {subLength}) The first part of a string. The last part of the string. |
trim({original}), ltrim({original}), rtrim({original}) Trim all whitespace, or on left or right side. |
upper({original}), lower({original}) UPPERCASE and lowercase. |
split({original}, {delimiter}) Split a string into a list of strings. |
reverse({original}) Reverse a string. |
length({string}) Calculate the number of characters in the string. |
Aggregation |
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count(*) The number of matching rows. |
count(variable) The number of non-NULL values. |
count(DISTINCT variable) All aggregation functions also take the DISTINCT modifier, which removes duplicates from the values. |
collect(n.property) List from the values, ignores NULL. |
sum(n.property) Sum numerical values. Similar functions are avg, min, max. |
percentileDisc(n.property, {percentile}) Discrete percentile. Continuous percentile is percentileCont. The percentile argument is from 0.0 to 1.0. |
stdev(n.property) Standard deviation for a sample of a population. For an entire population use stdevp. |
CASE |
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CASE n.eyes WHEN "blue" THEN 1 WHEN "brown" THEN 2 ELSE 3 END Return THEN value from the matching WHEN value. The ELSE value is optional, and substituted for NULL if missing. |
CASE WHEN n.eyes = "blue" THEN 1 WHEN n.age < 40 THEN 2 ELSE 3 END Return THEN value from the first WHEN predicate evaluating to TRUE. Predicates are evaluated in order. |
START |
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START n = node:nodeIndexName(key = {value}) Query the index named nodeIndexName with an exact query. Use node_auto_index for the automatic index. Note that other uses of START have been removed as of Cypher 2.2. |
CREATE UNIQUE |
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CREATE UNIQUE (n)-[:KNOWS]->(m {property: {value}}) Match pattern or create it if it does not exist. The pattern can not include any optional parts. |
Performance |
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