WITH

WITH子句可以获取并处理查询前半部分的结果，并将处理结果作为输入传递给查询的后半部分。

openCypher兼容性

本文操作仅适用于openCypher方式。

Note

在原生nGQL中，有与WITH类似的管道符，但它们的工作方式不同。不要在openCypher方式中使用管道符，也不要在原生nGQL中使用WITH子句。

组成复合查询

使用WITH子句可以组合语句，将一条语句的输出转换为另一条语句的输入。

示例1

  1. 匹配一个路径。
  2. 通过nodes()函数将路径上的所有点输出到一个列表。
  3. 将列表拆分为行。
  4. 去重后返回点的信息。
  1. nebula> MATCH p=(v:player{name:"Tim Duncan"})--() \
  2.         WITH nodes(p) AS n \
  3.         UNWIND n AS n1 \
  4.         RETURN DISTINCT n1;
  5. +-----------------------------------------------------------+
  6. | n1                                                        |
  7. +-----------------------------------------------------------+
  8. | ("player100" :player{age: 42, name: "Tim Duncan"})        |
  9. | ("player101" :player{age: 36, name: "Tony Parker"})       |
  10. | ("team204" :team{name: "Spurs"})                          |
  11. | ("player102" :player{age: 33, name: "LaMarcus Aldridge"}) |
  12. | ("player125" :player{age: 41, name: "Manu Ginobili"})     |
  13. | ("player104" :player{age: 32, name: "Marco Belinelli"})   |
  14. | ("player144" :player{age: 47, name: "Shaquille O'Neal"})  |
  15. | ("player105" :player{age: 31, name: "Danny Green"})       |
  16. | ("player113" :player{age: 29, name: "Dejounte Murray"})   |
  17. | ("player107" :player{age: 32, name: "Aron Baynes"})       |
  18. | ("player109" :player{age: 34, name: "Tiago Splitter"})    |
  19. | ("player108" :player{age: 36, name: "Boris Diaw"})        |
  20. +-----------------------------------------------------------+

示例2

  1. 匹配点ID为player100的点。
  2. 通过labels()函数将点的所有Tag输出到一个列表。
  3. 将列表拆分为行。
  4. 返回结果。
  1. nebula> MATCH (v) \
  2.         WHERE id(v)=="player100" \
  3.         WITH labels(v) AS tags_unf \
  4.         UNWIND tags_unf AS tags_f \
  5.         RETURN tags_f;
  6. +----------+
  7. | tags_f   |
  8. +----------+
  9. | "player" |
  10. +----------+

过滤聚合查询

WITH可以在聚合查询中作为过滤器使用。

  1. nebula> MATCH (v:player)-->(v2:player) \
  2.         WITH DISTINCT v2 AS v2, v2.age AS Age \
  3.         ORDER BY Age \
  4.         WHERE Age<25 \
  5.         RETURN v2.name AS Name, Age;
  6. +----------------------+-----+
  7. | Name                 | Age |
  8. +----------------------+-----+
  9. | "Luka Doncic"        | 20  |
  10. | "Ben Simmons"        | 22  |
  11. | "Kristaps Porzingis" | 23  |
  12. +----------------------+-----+

collect()之前处理输出

在collect()函数将输出结果转换为列表之前，可以使用WITH子句排序和限制输出结果。

  1. nebula> MATCH (v:player) \
  2.         WITH v.name AS Name \
  3.         ORDER BY Name DESC \
  4.         LIMIT 3 \
  5.         RETURN collect(Name);
  6. +-----------------------------------------------+
  7. | collect(Name)                                 |
  8. +-----------------------------------------------+
  9. | ["Yao Ming", "Vince Carter", "Tracy McGrady"] |
  10. +-----------------------------------------------+

结合RETURN语句使用

在WITH子句中设置别名，并通过RETURN子句输出结果。

  1. nebula> WITH [1, 2, 3] AS list  RETURN 3 IN list AS r;
  2. +------+
  3. | r    |
  4. +------+
  5. | true |
  6. +------+
  8. nebula> WITH 4 AS one, 3 AS two RETURN one > two AS result;
  9. +--------+
  10. | result |
  11. +--------+
  12. | true   |
  13. +--------+

最后更新: November 1, 2021