GROUP BY

GROUP BY子句可以用于聚合数据。

openCypher兼容性

本文操作仅适用于原生nGQL。

用户也可以使用openCypher方式的count()函数聚合数据。

  1. nebula>  MATCH (v:player)<-[:follow]-(:player) RETURN v.name AS Name, count(*) as cnt ORDER BY cnt DESC;
  2. +----------------------+-----+
  3. | Name                 | cnt |
  4. +----------------------+-----+
  5. | "Tim Duncan"         | 10  |
  6. | "LeBron James"       | 6   |
  7. | "Tony Parker"        | 5   |
  8. | "Chris Paul"         | 4   |
  9. | "Manu Ginobili"      | 4   |
  10. +----------------------+-----+
  11. ...

语法

GROUP BY子句可以聚合相同值的行，然后进行计数、排序和计算等操作。

GROUP BY子句可以在管道符（|）之后和YIELD子句之前使用。

  1. | GROUP BY <var> YIELD <var>, <aggregation_function(var)>

aggregation_function()函数支持avg()、sum()、max()、min()、count()、collect()、std()。

示例

  1. # 查找所有连接到player100的点，并根据他们的姓名进行分组，返回姓名的出现次数。
  2. nebula> GO FROM "player100" OVER follow BIDIRECT \
  3.         YIELD properties($$).name as Name \
  4.         | GROUP BY $-.Name \
  5.         YIELD $-.Name as Player, count(*) AS Name_Count;
  6. +---------------------+------------+
  7. | Player              | Name_Count |
  8. +---------------------+------------+
  9. | "Shaquille O'Neal"  | 1          |
  10. | "Tiago Splitter"    | 1          |
  11. | "Manu Ginobili"     | 2          |
  12. | "Boris Diaw"        | 1          |
  13. | "LaMarcus Aldridge" | 1          |
  14. | "Tony Parker"       | 2          |
  15. | "Marco Belinelli"   | 1          |
  16. | "Dejounte Murray"   | 1          |
  17. | "Danny Green"       | 1          |
  18. | "Aron Baynes"       | 1          |
  19. +---------------------+------------+

用函数进行分组和计算

  1. # 查找所有连接到player100的点，并根据起始点进行分组，返回degree的总和。
  2. nebula> GO FROM "player100" OVER follow \
  3.         YIELD src(edge) AS player, properties(edge).degree AS degree \
  4.         | GROUP BY $-.player \
  5.         YIELD sum($-.degree);
  6. +----------------+
  7. | sum($-.degree) |
  8. +----------------+
  9. | 190            |
  10. +----------------+

sum()函数详情请参见内置数学函数。

最后更新: November 1, 2021