ORDER BY

ORDER BY子句指定输出结果的排序规则。

  • 在nGQL扩展中，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。

  • 使用order by 的时候必须先定义别名才能使用，否则报错[ERROR (-12)]: SemanticError: Only column name can be used as sort item

排序规则分为如下两种：

  • ASC（默认）: 升序。
  • DESC: 降序。

nGQL扩展语法

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

示例

  1. nebula> FETCH PROP ON player "player100", "player101", "player102", "player103" \
  2.         YIELD player.age AS age, player.name AS name \
  3.         | ORDER BY age ASC, name DESC;
  4. +-------------+-----+---------------------+
  5. | VertexID    | age | name                |
  6. +-------------+-----+---------------------+
  7. | "player103" | 32  | "Rudy Gay"          |
  8. +-------------+-----+---------------------+
  9. | "player102" | 33  | "LaMarcus Aldridge" |
  10. +-------------+-----+---------------------+
  11. | "player101" | 36  | "Tony Parker"       |
  12. +-------------+-----+---------------------+
  13. | "player100" | 42  | "Tim Duncan"        |
  14. +-------------+-----+---------------------+

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. +-----------------+-----+
  8. | "Vince Carter"  | 42  |
  9. +-----------------+-----+
  10. | "Tracy McGrady" | 39  |
  11. +-----------------+-----+
  12. | "Tony Parker"   | 36  |
  13. +-----------------+-----+
  14. | "Tim Duncan"    | 42  |
  15. +-----------------+-----+
  16. ...
  18. # 首先以年龄排序，如果年龄相同，再以姓名排序。
  19. nebula> MATCH (v:player) RETURN v.age AS Age, v.name AS Name  \
  20.         ORDER BY Age DESC, Name ASC;
  21. +-----+-------------------+
  22. | Age | Name              |
  23. +-----+-------------------+
  24. | 47  | "Shaquille O'Neal" |
  25. +-----+-------------------+
  26. | 46  | "Grant Hill"      |
  27. +-----+-------------------+
  28. | 45  | "Jason Kidd"      |
  29. +-----+-------------------+
  30. | 45  | "Steve Nash"      |
  31. +-----+-------------------+
  32. ...

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. +-----------------+----------+
  9. | "Manu Ginobili" | 41       |
  10. +-----------------+----------+
  11. | "Spurs"         | __NULL__ |
  12. +-----------------+----------+
  14. nebula> MATCH (v:player{name:"Tim Duncan"}) --> (v2) \
  15.         RETURN v2.name AS Name, v2.age AS Age  \
  16.         ORDER BY Age DESC;
  17. +-----------------+----------+
  18. | Name            | Age      |
  19. +-----------------+----------+
  20. | "Spurs"         | __NULL__ |
  21. +-----------------+----------+
  22. | "Manu Ginobili" | 41       |
  23. +-----------------+----------+
  24. | "Tony Parker"   | 36       |
  25. +-----------------+----------+