RETURNGraph
RETURN
子句定义了nGQL查询的输出结果。如果需要返回多个字段,用英文逗号(,)分隔。
RETURN
可以引导子句或语句:
RETURN
子句可以用于nGQL中的openCypher方式语句中,例如MATCH
或UNWIND
。
RETURN
可以单独使用,输出表达式的结果。
openCypher兼容性Graph
本文操作仅适用于nGQL中的openCypher方式。关于原生nGQL如何定义输出结果,请参见Graph。
RETURN
不支持如下openCypher功能:
-
使用不在英文字母表中的字符作为变量名。例如:
MATCH (`点1`:player) \ RETURN `点1`;
-
设置一个模式,并返回该模式匹配的所有元素。例如:
MATCH (v:player) \ RETURN (v)-[e]->(v2);
历史版本兼容性Graph
- 在nGQL 1.x中,
RETURN
适用于原生nGQL,语法为RETURN <var_ref> IF <var_ref> IS NOT NULL
。
- 在nGQL 2.0中,
RETURN
不适用于原生nGQL。
Map顺序说明Graph
RETURN
返回Map时,Key的顺序是未定义的。
nebula> RETURN {age: 32, name: "Marco Belinelli"};
+------------------------------------+
| {age:32,name:"Marco Belinelli"} |
+------------------------------------+
| {age: 32, name: "Marco Belinelli"} |
+------------------------------------+
nebula> RETURN {zage: 32, name: "Marco Belinelli"};
+-------------------------------------+
| {zage:32,name:"Marco Belinelli"} |
+-------------------------------------+
| {name: "Marco Belinelli", zage: 32} |
+-------------------------------------+
返回点Graph
nebula> MATCH (v:player) \
RETURN v;
+---------------------------------------------------------------+
| v |
+---------------------------------------------------------------+
| ("player104" :player{age: 32, name: "Marco Belinelli"}) |
| ("player107" :player{age: 32, name: "Aron Baynes"}) |
| ("player116" :player{age: 34, name: "LeBron James"}) |
| ("player120" :player{age: 29, name: "James Harden"}) |
| ("player125" :player{age: 41, name: "Manu Ginobili"}) |
+---------------------------------------------------------------+
...
返回边Graph
nebula> MATCH (v:player)-[e]->() \
RETURN e;
+------------------------------------------------------------------------------+
| e |
+------------------------------------------------------------------------------+
| [:follow "player104"->"player100" @0 {degree: 55}] |
| [:follow "player104"->"player101" @0 {degree: 50}] |
| [:follow "player104"->"player105" @0 {degree: 60}] |
| [:serve "player104"->"team200" @0 {end_year: 2009, start_year: 2007}] |
| [:serve "player104"->"team208" @0 {end_year: 2016, start_year: 2015}] |
+------------------------------------------------------------------------------+
...
返回属性Graph
使用语法{<vertex_name>|<edge_name>}.<property>
返回点或边的属性。
nebula> MATCH (v:player) \
RETURN v.name, v.age \
LIMIT 3;
+-------------------+-------+
| v.name | v.age |
+-------------------+-------+
| "Rajon Rondo" | 33 |
| "Rudy Gay" | 32 |
| "Dejounte Murray" | 29 |
+-------------------+-------+
返回所有元素Graph
使用星号(*)返回匹配模式中的所有元素。
nebula> MATCH (v:player{name:"Tim Duncan"}) \
RETURN *;
+----------------------------------------------------+
| v |
+----------------------------------------------------+
| ("player100" :player{age: 42, name: "Tim Duncan"}) |
+----------------------------------------------------+
nebula> MATCH (v:player{name:"Tim Duncan"})-[e]->(v2) \
RETURN *;
+----------------------------------------------------+-----------------------------------------------------------------------+-------------------------------------------------------+
| v | e | v2 |
+----------------------------------------------------+-----------------------------------------------------------------------+-------------------------------------------------------+
| ("player100" :player{age: 42, name: "Tim Duncan"}) | [:follow "player100"->"player101" @0 {degree: 95}] | ("player101" :player{age: 36, name: "Tony Parker"}) |
| ("player100" :player{age: 42, name: "Tim Duncan"}) | [:follow "player100"->"player125" @0 {degree: 95}] | ("player125" :player{age: 41, name: "Manu Ginobili"}) |
| ("player100" :player{age: 42, name: "Tim Duncan"}) | [:serve "player100"->"team204" @0 {end_year: 2016, start_year: 1997}] | ("team204" :team{name: "Spurs"}) |
+----------------------------------------------------+-----------------------------------------------------------------------+-------------------------------------------------------+
重命名字段Graph
使用语法AS <alias>
重命名输出结果中的字段。
nebula> MATCH (v:player{name:"Tim Duncan"})-[:serve]->(v2) \
RETURN v2.name AS Team;
+---------+
| Team |
+---------+
| "Spurs" |
+---------+
nebula> RETURN "Amber" AS Name;
+---------+
| Name |
+---------+
| "Amber" |
+---------+
返回不存在的属性Graph
如果匹配的结果中,某个属性不存在,会返回NULL
。
nebula> MATCH (v:player{name:"Tim Duncan"})-[e]->(v2) \
RETURN v2.name, type(e), v2.age;
+-----------------+----------+--------------+
| v2.name | type(e) | v2.age |
+-----------------+----------+--------------+
| "Tony Parker" | "follow" | 36 |
| "Manu Ginobili" | "follow" | 41 |
| "Spurs" | "serve" | UNKNOWN_PROP |
+-----------------+----------+--------------+
返回表达式结果Graph
RETURN
语句可以返回字面量、函数或谓词等表达式的结果。
nebula> MATCH (v:player{name:"Tony Parker"})-->(v2:player) \
RETURN DISTINCT v2.name, "Hello"+" graphs!", v2.age > 35;
+---------------------+------------------+-------------+
| v2.name | (Hello+ graphs!) | (v2.age>35) |
+---------------------+------------------+-------------+
| "Tim Duncan" | "Hello graphs!" | true |
| "LaMarcus Aldridge" | "Hello graphs!" | false |
| "Manu Ginobili" | "Hello graphs!" | true |
+---------------------+------------------+-------------+
nebula> RETURN 1+1;
+-------+
| (1+1) |
+-------+
| 2 |
+-------+
nebula> RETURN 3 > 1;
+-------+
| (3>1) |
+-------+
| true |
+-------+
nebula> RETURN 1+1, rand32(1, 5);
+-------+-------------+
| (1+1) | rand32(1,5) |
+-------+-------------+
| 2 | 1 |
+-------+-------------+
返回唯一字段Graph
使用DISTINCT
可以删除结果集中的重复字段。
# 未使用DISTINCT。
nebula> MATCH (v:player{name:"Tony Parker"})--(v2:player) \
RETURN v2.name, v2.age;
+---------------------+--------+
| v2.name | v2.age |
+---------------------+--------+
| "Tim Duncan" | 42 |
| "LaMarcus Aldridge" | 33 |
| "Marco Belinelli" | 32 |
| "Boris Diaw" | 36 |
| "Dejounte Murray" | 29 |
| "Tim Duncan" | 42 |
| "LaMarcus Aldridge" | 33 |
| "Manu Ginobili" | 41 |
+---------------------+--------+
# 使用DISTINCT。
nebula> MATCH (v:player{name:"Tony Parker"})--(v2:player) \
RETURN DISTINCT v2.name, v2.age;
+---------------------+--------+
| v2.name | v2.age |
+---------------------+--------+
| "Tim Duncan" | 42 |
| "LaMarcus Aldridge" | 33 |
| "Marco Belinelli" | 32 |
| "Boris Diaw" | 36 |
| "Dejounte Murray" | 29 |
| "Manu Ginobili" | 41 |
+---------------------+--------+
最后更新: November 1, 2021