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¶
- 匹配一个路径。
- 通过
nodes()函数将路径上的所有点输出到一个列表。 - 将列表拆分为行。
- 去重后返回点的信息。
ngql
nebula> MATCH p=(v:player{name:"Tim Duncan"})--() \
WITH nodes(p) AS n \
UNWIND n AS n1 \
RETURN DISTINCT n1;
+-----------------------------------------------------------+
| n1 |
+-----------------------------------------------------------+
| ("player100" :player{age: 42, name: "Tim Duncan"}) |
| ("player101" :player{age: 36, name: "Tony Parker"}) |
| ("team204" :team{name: "Spurs"}) |
| ("player102" :player{age: 33, name: "LaMarcus Aldridge"}) |
| ("player125" :player{age: 41, name: "Manu Ginobili"}) |
| ("player104" :player{age: 32, name: "Marco Belinelli"}) |
| ("player144" :player{age: 47, name: "Shaquille O'Neal"}) |
| ("player105" :player{age: 31, name: "Danny Green"}) |
| ("player113" :player{age: 29, name: "Dejounte Murray"}) |
| ("player107" :player{age: 32, name: "Aron Baynes"}) |
| ("player109" :player{age: 34, name: "Tiago Splitter"}) |
| ("player108" :player{age: 36, name: "Boris Diaw"}) |
+-----------------------------------------------------------+
示例 2¶
- 匹配点 ID 为
player100的点。 - 通过
labels()函数将点的所有 Tag 输出到一个列表。 - 将列表拆分为行。
- 返回结果。
ngql
nebula> MATCH (v) \
WHERE id(v)=="player100" \
WITH labels(v) AS tags_unf \
UNWIND tags_unf AS tags_f \
RETURN tags_f;
+----------+
| tags_f |
+----------+
| "player" |
+----------+
过滤聚合查询¶
WITH可以在聚合查询中作为过滤器使用。
ngql
nebula> MATCH (v:player)-->(v2:player) \
WITH DISTINCT v2 AS v2, v2.player.age AS Age \
ORDER BY Age \
WHERE Age<25 \
RETURN v2.player.name AS Name, Age;
+----------------------+-----+
| Name | Age |
+----------------------+-----+
| "Luka Doncic" | 20 |
| "Ben Simmons" | 22 |
| "Kristaps Porzingis" | 23 |
+----------------------+-----+
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。
ngql
nebula> MATCH (v:player) \
WITH v.player.name AS Name \
ORDER BY Name DESC \
LIMIT 3 \
RETURN collect(Name);
+-----------------------------------------------+
| collect(Name) |
+-----------------------------------------------+
| ["Yao Ming", "Vince Carter", "Tracy McGrady"] |
+-----------------------------------------------+
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。
```ngql nebula> WITH [1, 2, 3] AS list RETURN 3 IN list AS r; +------+ | r | +------+ | true | +------+
nebula> WITH 4 AS one, 3 AS two RETURN one > two AS result; +--------+ | result | +--------+ | true | +--------+ ```