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. +---+
  8. | 2 |
  9. +---+
  10. | 1 |
  11. +---+
  13. nebula> UNWIND [1, 2, 1] AS a \
  14.         RETURN collect(a);
  15. +------------+
  16. | COLLECT(a) |
  17. +------------+
  18. | [1, 2, 1]  |
  19. +------------+
  21. nebula> UNWIND [1, 2, 1] AS a \
  22.         RETURN a, collect(a), size(collect(a));
  23. +---+------------+------------------+
  24. | a | COLLECT(a) | size(COLLECT(a)) |
  25. +---+------------+------------------+
  26. | 2 | [2]        | 1                |
  27. +---+------------+------------------+
  28. | 1 | [1, 1]     | 2                |
  29. +---+------------+------------------+
  31. # 降序排列，限制输出行数为3，然后将结果输出到列表中。
  32. nebula> UNWIND ["c", "b", "a", "d" ] AS p \
  33.         WITH p AS q \
  34.         ORDER BY q DESC LIMIT 3 \
  35.         RETURN collect(q);
  36. +-----------------+
  37. | COLLECT(q)      |
  38. +-----------------+
  39. | ["d", "c", "b"] |
  40. +-----------------+
  42. nebula> WITH [1, 1, 2, 2] AS coll \
  43.         UNWIND coll AS x \
  44.         WITH DISTINCT x \
  45.         RETURN collect(x) AS ss;
  46. +--------+
  47. | ss     |
  48. +--------+
  49. | [1, 2] |
  50. +--------+
  52. nebula> MATCH (n:player) \
  53.         RETURN collect(n.age);
  54. +---------------------------------------------------------------+
  55. | COLLECT(n.age)                                                |
  56. ----------------------------------------------------------------+
  57. | [32, 32, 34, 29, 41, 40, 33, 25, 40, 37, ...
  58. ...
  60. # 基于年龄聚合姓名。
  61. nebula> MATCH (n:player) \
  62.         RETURN n.age AS age, collect(n.name);
  63. +-----+--------------------------------------------------------------------------+
  64. | age | collect(n.name)                                                          |
  65. +-----+--------------------------------------------------------------------------+
  66. | 24  | ["Giannis Antetokounmpo"]                                                |
  67. +-----+--------------------------------------------------------------------------+
  68. | 20  | ["Luka Doncic"]                                                          |
  69. +-----+--------------------------------------------------------------------------+
  70. | 25  | ["Joel Embiid", "Kyle Anderson"]                                         |
  71. +-----+--------------------------------------------------------------------------+
  72. ...