比较符

Nebula Graph支持的比较符如下。

符号说明
=赋值
+加法
-减法
*乘法
/除法
==相等
!=, <>不等于
>大于
>=大于等于
<小于
<=小于等于
%取模
-负数符号
IS NULL为NULL
IS NOT NULL不为NULL
IS EMPTY不存在
IS NOT EMPTY存在

比较操作的结果是true或者false。

OpenCypher兼容性

  • NULL的比较操作和openCypher不同，行为也可能会改变。在openCypher中，IS [NOT] NULL通常与OPTIONAL MATCH一起使用，但是nGQL不支持OPTIONAL MATCH。

  • openCypher中没有EMPTY，因此不支持在MATCH语句中使用EMPTY。

示例

==

字符串比较时，会区分大小写。不同类型的值不相等。

  1. nebula> RETURN 'A' == 'a', toUpper('A') == toUpper('a'), toLower('A') == toLower('a');
  2. +------------+------------------------------+------------------------------+
  3. | ("A"=="a") | (toUpper("A")==toUpper("a")) | (toLower("A")==toLower("a")) |
  4. +------------+------------------------------+------------------------------+
  5. | false      | true                         | true                         |
  6. +------------+------------------------------+------------------------------+
  8. nebula> RETURN '2' == 2, toInteger('2') == 2;
  9. +----------+---------------------+
  10. | ("2"==2) | (toInteger("2")==2) |
  11. +----------+---------------------+
  12. | false    | true                |
  13. +----------+---------------------+

>

  1. nebula> RETURN 3 > 2;
  2. +-------+
  3. | (3>2) |
  4. +-------+
  5. | true  |
  6. +-------+
  8. nebula> WITH 4 AS one, 3 AS two \
  9.         RETURN one > two AS result;
  10. +--------+
  11. | result |
  12. +--------+
  13. | true   |
  14. +--------+

>=

  1. nebula> RETURN 2 >= "2", 2 >= 2;
  2. +----------+--------+
  3. | (2>="2") | (2>=2) |
  4. +----------+--------+
  5. | __NULL__ | true   |
  6. +----------+--------+

<

  1. nebula> YIELD 2.0 < 1.9;
  2. +---------+
  3. | (2<1.9) |
  4. +---------+
  5. | false   |
  6. +---------+

<=

  1. nebula> YIELD 0.11 <= 0.11;
  2. +--------------+
  3. | (0.11<=0.11) |
  4. +--------------+
  5. | true         |
  6. +--------------+

!=

  1. nebula> YIELD 1 != '1';
  2. +--------+
  3. | (1!=1) |
  4. +--------+
  5. | true   |
  6. +--------+

IS [NOT] NULL

  1. nebula> RETURN null IS NULL AS value1, null == null AS value2, null != null AS value3;
  2. +--------+----------+----------+
  3. | value1 | value2   | value3   |
  4. +--------+----------+----------+
  5. | true   | __NULL__ | __NULL__ |
  6. +--------+----------+----------+
  8. nebula> RETURN length(NULL), size(NULL), count(NULL), NULL IS NULL, NULL IS NOT NULL, sin(NULL), NULL + NULL, [1, NULL] IS NULL;
  9. +--------------+------------+-------------+--------------+------------------+-----------+-------------+------------------+
  10. | length(NULL) | size(NULL) | count(NULL) | NULL IS NULL | NULL IS NOT NULL | sin(NULL) | (NULL+NULL) | [1,NULL] IS NULL |
  11. +--------------+------------+-------------+--------------+------------------+-----------+-------------+------------------+
  12. | __NULL__     | __NULL__   | 0           | true         | false            | __NULL__  | __NULL__    | false            |
  13. +--------------+------------+-------------+--------------+------------------+-----------+-------------+------------------+
  15. nebula> WITH {name: null} AS map \
  16.         RETURN map.name IS NOT NULL;
  17. +----------------------+
  18. | map.name IS NOT NULL |
  19. +----------------------+
  20. | false                |
  21. +----------------------+
  23. nebula> WITH {name: 'Mats', name2: 'Pontus'} AS map1, \
  24.         {name: null} AS map2, {notName: 0, notName2: null } AS map3 \
  25.         RETURN map1.name IS NULL, map2.name IS NOT NULL, map3.name IS NULL;
  26. +-------------------+-----------------------+-------------------+
  27. | map1.name IS NULL | map2.name IS NOT NULL | map3.name IS NULL |
  28. +-------------------+-----------------------+-------------------+
  29. | false             | false                 | true              |
  30. +-------------------+-----------------------+-------------------+
  32. nebula> MATCH (n:player) \
  33.         RETURN n.age IS NULL, n.name IS NOT NULL, n.empty IS NULL;
  34. +---------------+--------------------+-----------------+
  35. | n.age IS NULL | n.name IS NOT NULL | n.empty IS NULL |
  36. +---------------+--------------------+-----------------+
  37. | false         | true               | true            |
  38. +---------------+--------------------+-----------------+
  39. | false         | true               | true            |
  40. +---------------+--------------------+-----------------+
  41. | false         | true               | true            |
  42. +---------------+--------------------+-----------------+
  43. ...

IS [NOT] EMPTY

  1. nebula> RETURN null IS EMPTY;
  2. +---------------+
  3. | NULL IS EMPTY |
  4. +---------------+
  5. | false         |
  6. +---------------+
  8. nebula> RETURN "a" IS NOT EMPTY;
  9. +------------------+
  10. | "a" IS NOT EMPTY |
  11. +------------------+
  12. | true             |
  13. +------------------+
  15. nebula> GO FROM "player100" OVER * WHERE $$.player.name IS NOT EMPTY YIELD follow._dst;
  16. +-------------+
  17. | follow._dst |
  18. +-------------+
  19. | "player125" |
  20. +-------------+
  21. | "player101" |
  22. +-------------+