标量函数

id(expression)

SELECT *
FROM cypher('graph_name', $$
    MATCH (a)
    RETURN id(a)
$$) as (id agtype);

   id        
--------
 0
 1
 2
 3
(4 rows)

start_id(expression)

SELECT *
FROM cypher('graph_name', $$
    MATCH ()-[e]->()
    RETURN start_id(e)
$$) as (start_id agtype);

   id        
--------
 0
 1
 2
 3
(4 rows)

end_id(expression)

SELECT *
FROM cypher('graph_name', $$
    MATCH ()-[e]->()
    RETURN end_id(e)
$$) as (end_id agtype);

   id        
--------
 4
 5
 6
 7
(4 rows)

type(edge)

SELECT *
FROM cypher('graph_name', $$
    MATCH ()-[e]->()
    RETURN type(e)
$$) as (type agtype);

    type        
-----------
 "KNOWS"
 "KNOWS"
(2 rows)

properties(expression)

SELECT *
FROM cypher('graph_name', $$
    CREATE (p:Person {name: 'Stefan', city: 'Berlin'})
    RETURN properties(p)
$$) as (properties agtype);

               properties                 
--------------------------------------
 {"city": "Berlin", "name": "Stefan"}
(1 row)

head(list)

SELECT *
FROM cypher('graph_name', $$
   MATCH (a)
   WHERE a.name = 'Eskil'
   RETURN a.array, head(a.array)
$$) as (lst agtype, lst_head agtype);

 lst                     | lst_head 
-------------------------+----------
 ["one","two","three"]   | "one"	
(1 row)

last(list)

SELECT *
FROM cypher('graph_name', $$
MATCH (a)
WHERE a.name = 'Eskil'
RETURN a.array, last(a.array)
$$) as (lst agtype, lst_tail agtype);

 lst                     | lst_tail 
-------------------------+----------
 ["one","two","three"]   | "three"	
(1 row)

length(path)

SELECT *
FROM cypher('graph_name', $$
   MATCH p = (a)-[]->(b)-[]->(c)
   WHERE a.name = 'Alice'
   RETURN length(p)
$$) as (length_of_path agtype);

 length_of_path 
----------------
 2
 2
 2
(3 rows)

size(list)

SELECT *
FROM cypher('graph_name', $$
    RETURN size(['Alice', 'Bob'])
$$) as (size_of_list agtype);

 size_of_list 
--------------
 2
(1 row)

startNode(edge)

SELECT *
FROM cypher('graph_name', $$
    MATCH (x:Developer)-[r]-()
    RETURN startNode(r)
$$) as (v agtype);

                     v 
--------------------------------------------
 Node[0]{name:"Alice",age:38,eyes:"brown"}
 Node[0]{name:"Alice",age:38,eyes:"brown"}
(2 rows)

endNode(edge)

SELECT *
FROM cypher('graph_name', $$
    MATCH (x:Developer)-[r]-()
    RETURN endNode(r)
$$) as (v agtype);

                     v 
--------------------------------------------
 Node[2]{name:"Charlie",age:53,eyes:"green"}
 Node[1]{name:"Bob",age:25,eyes:"blue"}
(2 rows)

timestamp()

SELECT *
FROM cypher('graph_name', $$
    RETURN timestamp()
$$) as (t agtype);

       t       
---------------
 1613496720760
(1 row)

toBoolean(expression)

SELECT *
FROM cypher('graph_name', $$
    RETURN toBoolean('TRUE'), toBoolean('not a boolean')
$$) as (a_bool agtype, not_a_bool agtype);

 a_bool | not_a_bool 
--------+------------
 true   | 
(1 row)

toFloat(expression)

SELECT *
FROM cypher('graph_name', $$
    RETURN toFloat('11.5'), toFloat('not a number')
$$) as (a_float agtype, not_a_float agtype);

 a_float | not_a_float 
---------+-------------
 11.5    | 
(1 row)

toInteger(expression)

SELECT *
FROM cypher('graph_name', $$
     RETURN toInteger('42'), toInteger('not a number')
$$) as (an_integer agtype, not_an_integer agtype);

 an_integer | not_an_integer 
------------+----------------
 42         | 
(1 row)

coalesce(expression [, expression]*)

SELECT *
FROM cypher('graph_name', $$
MATCH (a)
WHERE a.name = 'Alice'
RETURN coalesce(a.hairColor, a.eyes), a.hair_color, a.eyes
$$) as (color agtype, hair_color agtype, eyes agtype);

 color   | hair_color | eyes 
---------+------------+---------
 "brown" |            |	"Brown"
(1 row)