Nosql-neo4j-Cypher 函数 概要

目录： [TOC]

Cypher函数概要

• Cypher函数输入为null，输出也为null
• 函数输入是字符串时，输入的是unicode编码的字符，而不是char[]

断言函数Predicate functions

• 返回ture或者false

Function	Description
all()	Tests whether the predicate holds for all elements in a list.
any()	Tests whether the predicate holds for at least one element in a list.
exists()	Returns true if a match for the pattern exists in the graph, or if the specified property exists in the node, relationship or map.
none()	Returns true if the predicate holds for no element in a list.
single()	Returns true if the predicate holds for exactly one of the elements in a list.

标量函数Scalar functions

• 返回单个值

Function	Description
coalesce()	Returns the first non-null value in a list of expressions
endNode()	Returns the end node of a relationship.
head()	** Returns the first element** in a list.
id()	** Returns the id of a relationship or node**.
last()	Returns the last element in a list.
length()	Returns the length of a path.
properties()	Returns a map containing all the properties of a node or relationship.
randomUUID()	Returns a string value corresponding to a randomly-generated UUID.
size()	Returns the number of items in a list.
size() applied to pattern expression	Returns the number of sub-graphs matching the pattern expression.
size() applied to string	Returns the number of Unicode characters in a string.
startNode()	Returns the start node of a relationship.
timestamp()	Returns the difference, measured in milliseconds, between the current time and midnight, January 1, 1970 UTC.
toBoolean()	Converts a string value to a boolean value.
toFloat()	Converts an integer or string value to a floating point number.
toInteger()	Converts a floating point or string value to an integer value.
type()	Returns the string representation of the relationship type.

聚合函数Aggregating functions

Function	Description
avg() - Numeric values	Returns the average of a set of numeric values.
avg() - Durations	Returns the average of a set of Durations.
collect()	Returns a list containing the values returned by an expression.
count()	Returns the number of values or rows.
max()	Returns the maximum value in a set of values.
min()	Returns the minimum value in a set of values.
percentileCont()	Returns the percentile of a value over a group using linear interpolation.
percentileDisc()	Returns the nearest value to the given percentile over a group using a rounding method.
stDev()	Returns the standard deviation for the given value over a group for a sample of a population.
stDevP()	Returns the standard deviation for the given value over a group for an entire population.
sum() - Numeric values	Returns the sum of a set of numeric values.
sum() - Durations	Returns the sum of a set of Durations.

返回List函数List functions

Function	Description
keys()	Returns a list containing the string representations for all the property names of a node, relationship, or map.
labels()	Returns a list containing the string representations for all the labels of a node.
nodes()	Returns a list containing all the nodes in a path.
range()	Returns a list comprising all integer values within a specified range.
reduce()	Runs an expression against individual elements of a list, storing the result of the expression in an accumulator.
relationships()	Returns a list containing all the relationships in a path.
reverse()	Returns a list in which the order of all elements in the original list have been reversed.
tail()	Returns all but the first element in a list.

数值函数numeric functions

Function	Description
abs()	Returns the absolute value of a number.
ceil()	Returns the smallest floating point number that is greater than or equal to a number and equal to a mathematical integer.
floor()	Returns the largest floating point number that is less than or equal to a number and equal to a mathematical integer.
rand()	Returns a random floating point number in the range from 0 (inclusive) to 1 (exclusive); i.e. [0,1).
round()	Returns the value of a number rounded to the nearest integer.
sign()	Returns the signum of a number: 0 if the number is 0, -1 for any negative number, and 1 for any positive number.

对数函数logarithmic functions

Function	Description
e()	Returns the base of the natural logarithm, e.
exp()	Returns e^n, where e is the base of the natural logarithm, and n is the value of the argument expression.
log()	Returns the natural logarithm of a number.
log10()	Returns the common logarithm (base 10) of a number.
sqrt()	Returns the square root of a number.

三角函数trigonometric functions

Function	Description
acos()	Returns the arccosine of a number in radians.
asin()	Returns the arcsine of a number in radians.
atan()	Returns the arctangent of a number in radians.
atan2()	Returns the arctangent2 of a set of coordinates in radians.
cos()	Returns the cosine of a number.
cot()	Returns the cotangent of a number.
degrees()	Converts radians to degrees.
haversin()	Returns half the versine of a number.
pi()	Returns the mathematical constant pi.
radians()	Converts degrees to radians.
sin()	Returns the sine of a number.
tan()	Returns the tangent of a number.

字符串函数String functions

Function	Description
left()	Returns a string containing the specified number of leftmost characters of the original string.
lTrim()	Returns the original string with leading whitespace removed.
replace()	Returns a string in which all occurrences of a specified string in the original string have been replaced by another (specified) string.
reverse()	Returns a string in which the order of all characters in the original string have been reversed.
right()	Returns a string containing the specified number of rightmost characters of the original string.
rTrim()	Returns the original string with trailing whitespace removed.
split()	Returns a list of strings resulting from the splitting of the original string around matches of the given delimiter.
substring()	Returns a substring of the original string, beginning with a 0-based index start and length.
toLower()	Returns the original string in lowercase.
toString()	Converts an integer, float, boolean or temporal type (i.e. Date, Time, LocalTime, DateTime, LocalDateTime or Duration) value to a string.
toUpper()	Returns the original string in uppercase.
trim()	Returns the original string with leading and trailing whitespace removed.

时间函数Temporal functions

Function	Description
date()	Returns the current Date.
date.transaction()	Returns the current Date using the transaction clock.
date.statement()	Returns the current Date using the statement clock.
date.realtime()	Returns the current Date using the realtime clock.
date({year [, month, day]})	Returns a calendar (Year-Month-Day) Date.
date({year [, week, dayOfWeek]})	Returns a week (Year-Week-Day) Date.
date({year [, quarter, dayOfQuarter]})	Returns a quarter (Year-Quarter-Day) Date.
date({year [, ordinalDay]})	Returns an ordinal (Year-Day) Date.
date(string)	Returns a Date by parsing a string.
date({map})	Returns a Date from a map of another temporal value’s components.
date.truncate()	Returns a Date obtained by truncating a value at a specific component boundary. Truncation summary.
datetime()	Returns the current DateTime.
datetime.transaction()	Returns the current DateTime using the transaction clock.
datetime.statement()	Returns the current DateTime using the statement clock.
datetime.realtime()	Returns the current DateTime using the realtime clock.
datetime({year [, month, day, …]})	Returns a calendar (Year-Month-Day) DateTime.
datetime({year [, week, dayOfWeek, …]})	Returns a week (Year-Week-Day) DateTime.
datetime({year [, quarter, dayOfQuarter, …]})	Returns a quarter (Year-Quarter-Day) DateTime.
datetime({year [, ordinalDay, …]})	Returns an ordinal (Year-Day) DateTime.
datetime(string)	Returns a DateTime by parsing a string.
datetime({map})	Returns a DateTime from a map of another temporal value’s components.
datetime({epochSeconds})	Returns a DateTime from a timestamp.
datetime.truncate()	Returns a DateTime obtained by truncating a value at a specific component boundary. Truncation summary.
localdatetime()	Returns the current LocalDateTime.
localdatetime.transaction()	Returns the current LocalDateTime using the transaction clock.
localdatetime.statement()	Returns the current LocalDateTime using the statement clock.
localdatetime.realtime()	Returns the current LocalDateTime using the realtime clock.
localdatetime({year [, month, day, …]})	Returns a calendar (Year-Month-Day) LocalDateTime.
localdatetime({year [, week, dayOfWeek, …]})	Returns a week (Year-Week-Day) LocalDateTime.
localdatetime({year [, quarter, dayOfQuarter, …]})	Returns a quarter (Year-Quarter-Day) DateTime.
localdatetime({year [, ordinalDay, …]})	Returns an ordinal (Year-Day) LocalDateTime.
localdatetime(string)	Returns a LocalDateTime by parsing a string.
localdatetime({map})	Returns a LocalDateTime from a map of another temporal value’s components.
localdatetime.truncate()	Returns a LocalDateTime obtained by truncating a value at a specific component boundary. Truncation summary.
localtime()	Returns the current LocalTime.
localtime.transaction()	Returns the current LocalTime using the transaction clock.
localtime.statement()	Returns the current LocalTime using the statement clock.
localtime.realtime()	Returns the current LocalTime using the realtime clock.
localtime({hour [, minute, second, …]})	Returns a LocalTime with the specified component values.
localtime(string)	Returns a LocalTime by parsing a string.
localtime({time [, hour, …]})	Returns a LocalTime from a map of another temporal value’s components.
localtime.truncate()	Returns a LocalTime obtained by truncating a value at a specific component boundary. Truncation summary.
time()	Returns the current Time.
time.transaction()	Returns the current Time using the transaction clock.
time.statement()	Returns the current Time using the statement clock.
time.realtime()	Returns the current Time using the realtime clock.
time({hour [, minute, …]})	Returns a Time with the specified component values.
time(string)	Returns a Time by parsing a string.
time({time [, hour, …, timezone]})	Returns a Time from a map of another temporal value’s components.
time.truncate()	Returns a Time obtained by truncating a value at a specific component boundary. Truncation summary.

duration函数

Function	Description
duration({map})	Returns a Duration from a map of its components.
duration(string)	Returns a Duration by parsing a string.
duration.between()	Returns a Duration equal to the difference between two given instants.
duration.inMonths()	Returns a Duration equal to the difference in whole months, quarters or years between two given instants.
duration.inDays()	Returns a Duration equal to the difference in whole days or weeks between two given instants.
duration.inSeconds()	Returns a Duration equal to the difference in seconds and fractions of seconds, or minutes or hours, between two given instants.

坐标函数Spatial functions

Function	Description
distance()	Returns a floating point number representing the geodesic distance between any two points in the same CRS.
point() - Cartesian 2D	Returns a 2D point object, given two coordinate values in the Cartesian coordinate system.
point() - Cartesian 3D	Returns a 3D point object, given three coordinate values in the Cartesian coordinate system.
point() - WGS 84 2D	Returns a 2D point object, given two coordinate values in the WGS 84 geographic coordinate system.
point() - WGS 84 3D	Returns a 3D point object, given three coordinate values in the WGS 84 geographic coordinate system.

LOAD CSV functions

Function	Description
linenumber()	Returns the line number that LOAD CSV is currently using.
file()	Returns the absolute path of the file that LOAD CSV is using.

User-defined functions

User-defined functions are written in Java, deployed into the database and are called in the same way as any other Cypher function. There are two main types of functions that can be developed and used:

Type	Description	Usage	Developing
Scalar	For each row the function takes parameters and returns a result	Using UDF	Extending Neo4j (UDF)
Aggregating	Consumes many rows and produces an aggregated result	Using aggregating UDF	Extending Neo4j (Aggregating UDF)

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