collect函数

collect()函数返回一个符合表达式返回结果的列表。该函数可以将多条记录或值合并进一个列表，实现数据聚合。

collect()是一个聚合函数，类似SQL中的GROUP BY。

示例

  1. nebula> UNWIND [1, 2, 1] AS a \
  2.         RETURN a;
  3. +---+
  4. | a |
  5. +---+
  6. | 1 |
  7. | 2 |
  8. | 1 |
  9. +---+
  11. nebula> UNWIND [1, 2, 1] AS a \
  12.         RETURN collect(a);
  13. +------------+
  14. | collect(a) |
  15. +------------+
  16. | [1, 2, 1]  |
  17. +------------+
  19. nebula> UNWIND [1, 2, 1] AS a \
  20.         RETURN a, collect(a), size(collect(a));
  21. +---+------------+------------------+
  22. | a | collect(a) | size(COLLECT(a)) |
  23. +---+------------+------------------+
  24. | 2 | [2]        | 1                |
  25. | 1 | [1, 1]     | 2                |
  26. +---+------------+------------------+
  28. # 降序排列，限制输出行数为3，然后将结果输出到列表中。
  29. nebula> UNWIND ["c", "b", "a", "d" ] AS p \
  30.         WITH p AS q \
  31.         ORDER BY q DESC LIMIT 3 \
  32.         RETURN collect(q);
  33. +-----------------+
  34. | collect(q)      |
  35. +-----------------+
  36. | ["d", "c", "b"] |
  37. +-----------------+
  39. nebula> WITH [1, 1, 2, 2] AS coll \
  40.         UNWIND coll AS x \
  41.         WITH DISTINCT x \
  42.         RETURN collect(x) AS ss;
  43. +--------+
  44. | ss     |
  45. +--------+
  46. | [1, 2] |
  47. +--------+
  49. nebula> MATCH (n:player) \
  50.         RETURN collect(n.age);
  51. +---------------------------------------------------------------+
  52. | collect(n.age)                                                |
  53. +---------------------------------------------------------------+
  54. | [32, 32, 34, 29, 41, 40, 33, 25, 40, 37, ...
  55. ...
  57. # 基于年龄聚合姓名。
  58. nebula> MATCH (n:player) \
  59.         RETURN n.age AS age, collect(n.name);
  60. +-----+--------------------------------------------------------------------------+
  61. | age | collect(n.name)                                                          |
  62. +-----+--------------------------------------------------------------------------+
  63. | 24  | ["Giannis Antetokounmpo"]                                                |
  64. | 20  | ["Luka Doncic"]                                                          |
  65. | 25  | ["Joel Embiid", "Kyle Anderson"]                                         |
  66. +-----+--------------------------------------------------------------------------+
  67. ...

最后更新: October 27, 2021