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.
| Type | Description |
|---|---|
Null | Property has no value, which is the same as if the property doesn't exist. |
String | A character string (text). |
Boolean | A boolean value, either true or false. |
Integer | An integer number. |
Float | A floating-point number (real number). |
List | A list containing any number of property values of any supported type under a single property name. |
Map | A mapping of string keys to values of any supported type. |
Duration | A period of time. |
Date | A date with year, month, and day. |
LocalTime | Time without the time zone. |
LocalDateTime | Date and time without the time zone. |
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";
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.
| name | description |
|---|---|
| D | Days |
| H | Hours |
| M | Minutes |
| S | Seconds |
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:
| name | description |
|---|---|
| day | Converts all the microseconds back to days and returns the value. |
| hour | Subtracts days and returns the leftover value as hours. |
| minute | Subtracts the days and returns the leftover value as minutes. |
| second | Subtracts the days and returns the leftover value as seconds. |
| millisecond | Subtracts the days and returns the leftover value as milliseconds. |
| microsecond | Subtracts the days and returns the leftover value as microseconds. |
| nanosecond | Subtracts 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.
| name | description |
|---|---|
| Y | Year |
| M | Month |
| D | Day |
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:
| name | description |
|---|---|
| year | Returns the year field |
| month | Returns the month field |
| day | Returns 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.
| name | description |
|---|---|
| h | Hours |
| m | Minutes |
| s | Seconds |
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:
| name | description |
|---|---|
| hour | Returns the hour field |
| minute | Returns the minute field |
| second | Returns the second field |
| millisecond | Returns the millisecond field |
| microsecond | Returns 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.
| name | description |
|---|---|
| Y | Year |
| M | Month |
| D | Day |
| h | Hours |
| m | Minutes |
| s | Seconds |
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:
| name | description |
|---|---|
| year | Returns the year field |
| month | Returns the month field |
| day | Returns the day field |
| hour | Returns the hour field |
| minute | Returns the minute field |
| second | Returns the second field |
| millisecond | Returns the millisecond field |
| microsecond | Returns 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:
| op | result |
|---|---|
| Duration + Duration | Duration |
| Duration - Duration | Duration |
| - Duration | Duration |
Date operations:
| op | result |
|---|---|
| Date + Duration | Date |
| Duration + Date | Date |
| Date - Duration | Date |
| Date - Date | Duration |
LocalTime operations:
| op | result |
|---|---|
| LocalTime + Duration | LocalTime |
| Duration + LocalTime | LocalTime |
| LocalTime - Duration | LocalTime |
| LocalTime - LocalTime | Duration |
LocalDateTime operations:
| operation | result |
|---|---|
| LocalDateTime + Duration | LocalDateTime |
| Duration + LocalTateTime | LocalDateTime |
| LocalDateTime - Duration | LocalDateTime |
| LocalDateTime - LocalDateTime | Duration |
Procedures API
Data types are also used within query modules. Check out the documentation for the Python API, C API and C++ API.