谓词函数

    Nebula Graph支持以下谓词函数。

    如果列表为空，或者列表中的所有元素都为空，则返回NULL。

    在 openCypher 中只定义了函数exists()，其他几个函数依赖于具体实现。

    示例

    1. nebula> RETURN any(n IN [1, 2, 3, 4, 5, NULL] \
    2.         WHERE n > 2) AS r;
    3. +------+
    4. | r    |
    5. +------+
    6. | true |
    7. +------+
    9. nebula> RETURN single(n IN range(1, 5) \
    10.         WHERE n == 3) AS r;
    11. +------+
    12. | r    |
    13. +------+
    14. | true |
    15. +------+
    18.         WHERE n == 0) AS r;
    19. +------+
    20. | r    |
    21. +------+
    22. | true |
    23. +------+
    25.         RETURN any(n IN a WHERE n > 2);
    26. +-------------------------+
    27. | any(n IN a WHERE (n>2)) |
    28. +-------------------------+
    29. | true                    |
    30. +-------------------------+
    32. nebula> MATCH p = (n:player{name:"LeBron James"})<-[:follow]-(m) \
    33.         RETURN nodes(p)[0].name AS n1, nodes(p)[1].name AS n2, \
    34.         all(n IN nodes(p) WHERE n.name NOT STARTS WITH "D") AS b;
    35. +----------------+-------------------+-------+
    36. | n1             | n2                | b     |
    37. +----------------+-------------------+-------+
    38. | "LeBron James" | "Danny Green"     | false |
    39. +----------------+-------------------+-------+
    40. | "LeBron James" | "Dejounte Murray" | false |
    41. +----------------+-------------------+-------+
    42. | "LeBron James" | "Chris Paul"      | true  |
    43. +----------------+-------------------+-------+
    44. | "LeBron James" | "Kyrie Irving"    | true  |
    45. +----------------+-------------------+-------+
    47. +----------------+-------------------+-------+
    48. | "LeBron James" | "Dwyane Wade"     | false |
    49. +----------------+-------------------+-------+
    51.         RETURN single(n IN nodes(p) WHERE n.age > 40) AS b;
    52. +------+
    53. | b    |
    54. +------+
    55. | true |
    56. +------+
    58. nebula> MATCH (n:player) \
    59.         RETURN exists(n.id), n IS NOT NULL;
    60. +--------------+---------------+
    61. | exists(n.id) | n IS NOT NULL |
    62. +--------------+---------------+
    63. | false        | true          |
    64. +--------------+---------------+
    65. ...
    67. nebula> MATCH (n:player) \
    68.         WHERE exists(n['name']) RETURN n;
    69. +-------------------------------------------------------------------------------------------------------------+
    70. | n                                                                                                           |
    71. +-------------------------------------------------------------------------------------------------------------+
    72. | ("Grant Hill" :player{age: 46, name: "Grant Hill"})                                                         |
    73. +-------------------------------------------------------------------------------------------------------------+
    74. | ("Marc Gasol" :player{age: 34, name: "Marc Gasol"})                                                         |
    76. ...