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Version: 2.8.0

Data types

Since Memgraph is a graph database management system, data is stored in the form of graph elements: nodes and relationships. Each graph element can contain various types of data. This page describes which data types are supported in Memgraph.

Node labels & relationship types​

Nodes can have labels that are used to label or group nodes. A label is of the type String, and each node can have none or multiple labels. Labels can be changed at any time.

Relationships have a type, also represented in the form of a String. Unlike nodes, relationships must have exactly one relationship type and once it is set upon creation, it can never be modified again.

Property types​

Nodes and relationships can store various properties. Properties are similar to mappings or tables containing property names and their accompanying values. Property names are represented as text, while values can be of different types.

Each property can store a single value, and it is not possible to have multiple properties with the same name on a single graph element. But, the same property names can be found across multiple graph elements.

Also, there are no restrictions on the number of properties that can be stored in a single graph element. The only restriction is that the values must be of the supported types. Below is a table of supported data types.

TypeDescription
NullProperty has no value, which is the same as if the property doesn't exist.
StringA character string (text).
BooleanA boolean value, either true or false.
IntegerAn integer number.
FloatA floating-point number (real number).
ListA list containing any number of property values of any supported type under a single property name.
MapA mapping of string keys to values of any supported type.
DurationA period of time.
DateA date with year, month, and day.
LocalTimeTime without the time zone.
LocalDateTimeDate and time without the time zone.
note

If you want to modify List and Map property values, you need to replace them entirely.

The following queries are valid:

CREATE (:Node {property: [1, 2, 3]});
CREATE (:Node {property: {key: "value"}});

But these are not:

MATCH (n:Node) SET n.property[0] = 0;
MATCH (n:Node) SET n.property.key = "other value";

Maps​

The Cypher query language supports constructing and working with map values.

Literal maps​

It is possible to explicitly construct maps by stating key-value pairs:

RETURN {key: 'Value', listKey: [{inner: 'Map1'}, {inner: 'Map2'}]}

Map projection​

Cypher’s map projection syntax allows for easily constructing map projections from nodes, relationships, other map values, and all other values that have properties.

A map projection begins with the variable bound to the graph entity that’s to be projected from, and contains a body of comma-separated map elements enclosed by { and }.

map_variable {map_element, [, ...n]}

A map element projects one or more key-value pairs to the map projection. There are four different types of map projection elements:

  • Property selector: Projects the property name as the key, and the value of map_variable.property as the value for the projection.
  • All-properties selector: Projects all key-value pairs from the map_variable value.
  • Literal entry: This is a key-value pair, with the value being an arbitrary expression: key: <expression>.
  • Variable selector: Projects a variable: the variable name is the key, and the value it is pointing to is the value of the projection: <variable>.

The following conditions apply:

  • If map_variable points to a null value, its projected values will be null.
  • As with literal maps, key names must be strings.

Examples​

The following graph is used by all examples here:

Find Jennifer Lawrence and return data about her and the movies she’s acted in. This example contains a map projection with a literal entry, which in turn also uses map projection inside collect().

MATCH (actor:Person {name: 'Jennifer Lawrence'})-[:ACTED_IN]->(movie:Movie)
WITH actor, collect(movie {.title, .year}) AS movies
RETURN actor {.name, roles: movies} AS jennifer

The below query finds all Person nodes that have one or more relationships of type ACTED_IN connected to Movie nodes and returns the number of movies each Person has starred in. This example introduces the variable selector and uses it to project the movie count.

MATCH (actor:Person)-[:ACTED_IN]->(movie:Movie)
WITH actor, count(movie) AS nMovies
RETURN actor {.name, nMovies}

Finally, the next query returns all properties from the Bradley Cooper node. It uses an all-properties selector to project node properties, and in addition explicitly projects the dateOfBirth property. Since this property does not exist, a null value is projected in its place.

MATCH (actor:Person {name: 'Bradley Cooper'})
RETURN actor {.*, .dateOfBirth} as bradley

Temporal types​

Duration​

You can create a property of temporal type Duration from a string or a map by calling the function duration.

For strings, the duration format is: P[nD]T[nH][nM][nS] where n stands for a number, and the capital letters are used as a separator with each field in [] marked optional. For strings, Memgraph only allows the last field to be a double, e.g., P2DT2.5H. However, for maps, every field can be a double, an int or a mixture of both. Memgraph also supports negative durations.

namedescription
DDays
HHours
MMinutes
SSeconds

Example:

CREATE (:F1Laps {lap: duration("PT2M2.33S")});

Maps can contain the following six fields: day, hour, minute, second, millisecond and microsecond.

Example:

CREATE (:F1Laps {lap: duration({minute:2, second:2, microsecond:33})});

At this point, it must be pointed out that durations internally hold microseconds. Each of the fields specified above is first converted to microseconds and then reduced by addition to a single value. This has an interesting use case:

CREATE (:F1Laps {lap: duration({minute:2, second:-2, microsecond:-33})});

This converts minutes, seconds to microseconds and effectively produces the following equation: minutes - seconds - microseconds.

Each of the individual fields of a duration can be accessed through its properties as follows:

namedescription
dayConverts all the microseconds back to days and returns the value.
hourSubtracts days and returns the leftover value as hours.
minuteSubtracts the days and returns the leftover value as minutes.
secondSubtracts the days and returns the leftover value as seconds.
millisecondSubtracts the days and returns the leftover value as milliseconds.
microsecondSubtracts the days and returns the leftover value as microseconds.
nanosecondSubtracts the days and returns the leftover value as nanoseconds.

Example:

CREATE (:F1Laps {lap: duration({day:1, hour: 2, minute:3, second:4})});
MATCH (f:F1Laps) RETURN f.lap.day;
// Result
>> 1
MATCH (f:F1Laps) RETURN f.lap.hour;
// Result
>> 2
MATCH (f:F1Laps) RETURN f.lap.minute;
// Result
>> 123 // The value without days is 2 hours and 3  minutes, that is 123 minutes
MATCH (f:F1Laps) RETURN f.lap.second;
// Result
>> 7384 // The value without days is 2 hours, 3 minutes and 4 seconds, that is 7384 minutes

Date​

You can create a property of temporal type Date from a string or map by calling the function Date. For strings, the date format is specified by the ISO 8601: YYYY-MM-DD or YYYYMMDD or YYYY-MM.

namedescription
YYear
MMonth
DDay

The smallest year is 0 and the highest is 9999.

You can call date without arguments. This effectively sets the date field to the current date of the calendar (UTC clock).

Example:

CREATE (:Person {birthday: date("1947-07-30")});

For maps, three fields are available: year, month, day.

Example:

CREATE (:Person {birthday: date({year:1947, month:7, day:30})});

You can access the individual fields of a date through its properties:

namedescription
yearReturns the year field
monthReturns the month field
dayReturns the day field

Example:

MATCH (b:Person) RETURN b.birthday.year;

LocalTime​

You can create a property of temporal type LocalTime from a string or map by calling the function localTime. For strings, the local time format is specified by the ISO 8601: [T]hh:mm:ss or [T]hh:mm or [T]hhmmss or [T]hhmm or [T]hh.

namedescription
hHours
mMinutes
sSeconds

seconds can be defined as decimal fractions with up to 6 digits. The first 3 digits represent milliseconds, and the last 3 digits microseconds. For example, the string T22:10:32.300600 specifies 300 milliseconds and 600 microseconds.

You can call localTime without arguments. This effectively sets the time field to the current time of the calendar (UTC clock).

Example:

CREATE (:School {Calculus: localTime("09:15:00")});

For maps, there are 5 fields available: hour, minute, second, millisecond and microsecond.

Example:

CREATE (:School {Calculus: localTime({hour:9, minute:15})});

You can access the individual fields of a LocalTime through its properties:

namedescription
hourReturns the hour field
minuteReturns the minute field
secondReturns the second field
millisecondReturns the millisecond field
microsecondReturns the microsecond field

Example:

MATCH (s:School) RETURN s.Calculus.hour;

LocalDateTime​

You can create a property of temporal type LocalDateTime from a string or map by calling the function localDateTime. For strings, the local time format is specified by the ISO 8601: YYYY-MM-DDThh:mm:ss or YYYY-MM-DDThh:mm or YYYYMMDDThhmmss or YYYYMMDDThhmm or YYYYMMDDThh.

namedescription
YYear
MMonth
DDay
hHours
mMinutes
sSeconds

You can call localDateTime without arguments. This effectively sets the date and time fields to the current date and time of the calendar (UTC clock). Example:

CREATE (:Flights {AIR123: localDateTime("2021-10-05T14:15:00")});

For maps the following fields are available: year, month, day, hour, minute, second, millisecond and microsecond.

Example:

CREATE (:Flights {AIR123: localDateTime({year:2021, month:10, day:5, hour:14, minute:15})});

You can access the individual fields of LocalDateTime through its properties:

namedescription
yearReturns the year field
monthReturns the month field
dayReturns the day field
hourReturns the hour field
minuteReturns the minute field
secondReturns the second field
millisecondReturns the millisecond field
microsecondReturns the microsecond field

Example:

MATCH (f:Flights) RETURN f.AIR123.year;

Temporal types arithmetic​

Temporal types Duration, Date, LocalTime and LocalDateTime support native arithmetic, and the operations are summarized in the following table:

Duration operations:

opresult
Duration + DurationDuration
Duration - DurationDuration
- DurationDuration

Date operations:

opresult
Date + DurationDate
Duration + DateDate
Date - DurationDate
Date - DateDuration

LocalTime operations:

opresult
LocalTime + DurationLocalTime
Duration + LocalTimeLocalTime
LocalTime - DurationLocalTime
LocalTime - LocalTimeDuration

LocalDateTime operations:

operationresult
LocalDateTime + DurationLocalDateTime
Duration + LocalTateTimeLocalDateTime
LocalDateTime - DurationLocalDateTime
LocalDateTime - LocalDateTimeDuration

Procedures API​

Data types are also used within query modules. Check out the documentation for the Python API, C API and C++ API.