ORDER BY

ORDER BY子句指定输出结果的排序规则。

  • 在原生nGQL中，必须在YIELD子句之后使用管道符（|）和ORDER BY子句。

  • 在openCypher方式中，不允许使用管道符。在RETURN子句之后使用ORDER BY子句。

排序规则分为如下两种：

  • ASC（默认）: 升序。
  • DESC: 降序。

原生nGQL语法

  1. <YIELD clause>
  2. ORDER BY <expression> [ASC | DESC] [, <expression> [ASC | DESC] ...];

Compatibility

原生nGQL语法中，ORDER BY命令后必须使用引用符$-.。但在2.5.0之前的版本中不需要。

示例

  1. nebula> FETCH PROP ON player "player100", "player101", "player102", "player103" \
  2.         YIELD properties(vertex).age AS age, properties(vertex).name AS name \
  3.         | ORDER BY $-.age ASC, $-.name DESC;
  4. +-------------+-----+---------------------+
  5. | VertexID    | age | name                |
  6. +-------------+-----+---------------------+
  7. | "player103" | 32  | "Rudy Gay"          |
  8. | "player102" | 33  | "LaMarcus Aldridge" |
  9. | "player101" | 36  | "Tony Parker"       |
  10. | "player100" | 42  | "Tim Duncan"        |
  11. +-------------+-----+---------------------+
  13. nebula> $var = GO FROM "player100" OVER follow \
  14.         YIELD dst(edge) AS dst; \
  15.         ORDER BY $var.dst DESC;
  16. +-------------+
  17. | dst         |
  18. +-------------+
  19. | "player125" |
  20. | "player101" |
  21. +-------------+

OpenCypher方式语法

  1. <RETURN clause>
  2. ORDER BY <expression> [ASC | DESC] [, <expression> [ASC | DESC] ...];

示例

  1. nebula> MATCH (v:player) RETURN v.name AS Name, v.age AS Age  \
  2.         ORDER BY Name DESC;
  3. +-----------------+-----+
  4. | Name            | Age |
  5. +-----------------+-----+
  6. | "Yao Ming"      | 38  |
  7. | "Vince Carter"  | 42  |
  8. | "Tracy McGrady" | 39  |
  9. | "Tony Parker"   | 36  |
  10. | "Tim Duncan"    | 42  |
  11. +-----------------+-----+
  12. ...
  14. # 首先以年龄排序，如果年龄相同，再以姓名排序。
  15. nebula> MATCH (v:player) RETURN v.age AS Age, v.name AS Name  \
  16.         ORDER BY Age DESC, Name ASC;
  17. +-----+-------------------+
  18. | Age | Name              |
  19. +-----+-------------------+
  20. | 47  | "Shaquille O'Neal" |
  21. | 46  | "Grant Hill"      |
  22. | 45  | "Jason Kidd"      |
  23. | 45  | "Steve Nash"      |
  24. +-----+-------------------+
  25. ...

NULL值的排序

升序排列时，会在输出的最后列出NULL值，降序排列时，会在输出的开头列出NULL值。

  1. nebula> MATCH (v:player{name:"Tim Duncan"}) --> (v2) \
  2.         RETURN v2.name AS Name, v2.age AS Age  \
  3.         ORDER BY Age;
  4. +-----------------+--------------+
  5. | Name            | Age          |
  6. +-----------------+--------------+
  7. | "Tony Parker"   | 36           |
  8. | "Manu Ginobili" | 41           |
  9. | "Spurs"         | UNKNOWN_PROP |
  10. +-----------------+--------------+
  12. nebula> MATCH (v:player{name:"Tim Duncan"}) --> (v2) \
  13.         RETURN v2.name AS Name, v2.age AS Age  \
  14.         ORDER BY Age DESC;
  15. +-----------------+--------------+
  16. | Name            | Age          |
  17. +-----------------+--------------+
  18. | "Spurs"         | UNKNOWN_PROP |
  19. | "Manu Ginobili" | 41           |
  20. | "Tony Parker"   | 36           |
  21. +-----------------+--------------+

最后更新: November 1, 2021