apoc.agg.nth
函数

详细信息
语法	`apoc.agg.nth(value, offset)`
描述	返回给定集合中的第 n 个值（若要获取未知长度集合的最后一项，可以使用 -1）。
参数	名称	类型	描述
	`值`	`ANY`	要聚合的值。
	`offset`	`INTEGER（整数）`	要返回的值的索引，或使用 -1 返回最后一项。
返回	`ANY`

用法示例

本节中的示例基于以下示例图

CREATE (Keanu:Person {name:'Keanu Reeves', born:1964})
CREATE (TomH:Person {name:'Tom Hanks', born:1956})

CREATE (TheMatrix:Movie {title:'The Matrix', released:1999, tagline:'Welcome to the Real World'})
CREATE (TheMatrixReloaded:Movie {title:'The Matrix Reloaded', released:2003, tagline:'Free your mind'})
CREATE (TheMatrixRevolutions:Movie {title:'The Matrix Revolutions', released:2003, tagline:'Everything that has a beginning has an end'})
CREATE (YouveGotMail:Movie {title:"You've Got Mail", released:1998, tagline:'At odds in life... in love on-line.'})
CREATE (SleeplessInSeattle:Movie {title:'Sleepless in Seattle', released:1993, tagline:'What if someone you never met, someone you never saw, someone you never knew was the only someone for you?'})

CREATE (Keanu)-[:ACTED_IN {roles:['Neo']}]->(TheMatrix)
CREATE (Keanu)-[:ACTED_IN {roles:['Neo']}]->(TheMatrixReloaded)
CREATE (Keanu)-[:ACTED_IN {roles:['Neo']}]->(TheMatrixRevolutions)

CREATE (TomH)-[:ACTED_IN {roles:['Joe Fox']}]->(YouveGotMail)
CREATE (TomH)-[:ACTED_IN {roles:['Sam Baldwin']}]->(SleeplessInSeattle);

apoc.agg.nth

MATCH (p:Person)-[:ACTED_IN]->(movie)
WITH p, movie
ORDER BY p, movie.released
RETURN p.name AS person, apoc.agg.nth(movie, 1) AS nthMovie

使用 Cypher 的 OFFSET 和 LIMIT

MATCH (p:Person)
CALL (p) {
  MATCH (p)-[:ACTED_IN]->(movie)
  RETURN movie ORDER BY p, movie.released OFFSET 1 LIMIT 1
}
RETURN p.name AS person, movie AS nthMovie

结果
person	nthMovie
"Keanu Reeves"	(:Movie {tagline: "Free your mind", title: "The Matrix Reloaded", released: 2003})
"Tom Hanks"	(:Movie {tagline: "At odds in life… in love on-line.", title: "You’ve Got Mail", released: 1998})