nGQL 风格指南¶
nGQL 没有严格的构建格式要求,但根据恰当而统一的风格创建 nGQL 语句有利于提高可读性、避免歧义。在同一组织或项目中使用相同的 nGQL 风格有利于降低维护成本,规避因格式混乱或误解造成的问题。本文为写作 nGQL 语句提供了风格参考。
Compatibility
nGQL 风格与 Cypher Style Guide 不同。
换行¶
-
换行写子句。
不推荐:
GO FROM "player100" OVER follow REVERSELY YIELD src(edge) AS id;
推荐:
GO FROM "player100" \ OVER follow REVERSELY \ YIELD src(edge) AS id;
-
换行写复合语句中的不同语句。
不推荐:
GO FROM "player100" OVER follow REVERSELY YIELD src(edge) AS id | GO FROM $-.id \ OVER serve WHERE properties($^).age > 20 YIELD properties($^).name AS FriendOf, properties($$).name AS Team;
推荐:
GO FROM "player100" \ OVER follow REVERSELY \ YIELD src(edge) AS id | \ GO FROM $-.id OVER serve \ WHERE properties($^).age > 20 \ YIELD properties($^).name AS FriendOf, properties($$).name AS Team;
-
子句长度超过 80 个字符时,在合适的位置换行。
不推荐:
MATCH (v:player{name:"Tim Duncan"})-[e]->(v2) \ WHERE (v2.player.name STARTS WITH "Y" AND v2.player.age > 35 AND v2.player.age < v.player.age) OR (v2.player.name STARTS WITH "T" AND v2.player.age < 45 AND v2.player.age > v.player.age) \ RETURN v2;
推荐:
MATCH (v:player{name:"Tim Duncan"})-[e]->(v2) \ WHERE (v2.player.name STARTS WITH "Y" AND v2.player.age > 35 AND v2.player.age < v.player.age) \ OR (v2.player.name STARTS WITH "T" AND v2.player.age < 45 AND v2.player.age > v.player.age) \ RETURN v2;
Note
即使子句不超过 80 个字符,如需换行后有助于理解,也可将子句再次分行。
标识符命名¶
在 nGQL 语句中,关键字、标点符号、空格以外的字符内容都是标识符。推荐的标识符命名方式如下。
-
使用单数名词命名 Tag,用原型动词或动词短语构成 Edge type。
不推荐:
MATCH p=(v:players)-[e:are_following]-(v2) \ RETURN nodes(p);
推荐:
MATCH p=(v:player)-[e:follow]-(v2) \ RETURN nodes(p);
-
标识符用蛇形命名法,以下划线(_)连接单词,且所有字母小写。
不推荐:
MATCH (v:basketballTeam) \ RETURN v;
推荐:
MATCH (v:basketball_team) \ RETURN v;
-
语法关键词大写,变量小写。
不推荐:
match (V:player) return V limit 5;
推荐:
MATCH (v:player) RETURN v LIMIT 5;
Pattern¶
-
分行写 Pattern 时,在表示边的箭头右侧换行,而不是左侧。
不推荐:
MATCH (v:player{name: "Tim Duncan", age: 42}) \ -[e:follow]->()-[e2:serve]->()<--(v2) \ RETURN v, e, v2;
推荐:
MATCH (v:player{name: "Tim Duncan", age: 42})-[e:follow]-> \ ()-[e2:serve]->()<--(v2) \ RETURN v, e, v2;
-
将无需查询的点和边匿名化。
不推荐:
MATCH (v:player)-[e:follow]->(v2) \ RETURN v;
推荐:
MATCH (v:player)-[:follow]->() \ RETURN v;
-
将非匿名点放在匿名点的前面。
不推荐:
MATCH ()-[:follow]->(v) \ RETURN v;
推荐:
MATCH (v)<-[:follow]-() \ RETURN v;
字符串¶
字符串用双引号包围。
不推荐:
RETURN 'Hello Nebula!';
推荐:
RETURN "Hello Nebula!\"123\"";
Note
字符串中需要嵌套单引号或双引号时,用反斜线(\)转义。例如:
RETURN "\"NebulaGraph is amazing,\" the user says.";
结束语句¶
-
用英文分号(;)结束 nGQL 语句。
不推荐:
FETCH PROP ON player "player100" YIELD properties(vertex)
推荐:
FETCH PROP ON player "player100" YIELD properties(vertex);
-
使用管道符(|)分隔的复合语句,仅在最后一行末用英文分号结尾。在管道符前使用英文分号会导致语句执行失败。
不支持:
GO FROM "player100" \ OVER follow \ YIELD dst(edge) AS id; | \ GO FROM $-.id \ OVER serve \ YIELD properties($$).name AS Team, properties($^).name AS Player;
支持:
GO FROM "player100" \ OVER follow \ YIELD dst(edge) AS id | \ GO FROM $-.id \ OVER serve \ YIELD properties($$).name AS Team, properties($^).name AS Player;
-
在包含自定义变量的复合语句中,用英文分号结束定义变量的语句。不按规则加分号或使用管道符结束该语句会导致执行失败。
不支持:
$var = GO FROM "player100" \ OVER follow \ YIELD dst(edge) AS id \ GO FROM $var.id \ OVER serve \ YIELD properties($$).name AS Team, properties($^).name AS Player;
也不支持:
$var = GO FROM "player100" \ OVER follow \ YIELD dst(edge) AS id | \ GO FROM $var.id \ OVER serve \ YIELD properties($$).name AS Team, properties($^).name AS Player;
支持:
$var = GO FROM "player100" \ OVER follow \ YIELD dst(edge) AS id; \ GO FROM $var.id \ OVER serve \ YIELD properties($$).name AS Team, properties($^).name AS Player;
最后更新:
September 4, 2023