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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

<YIELD clause>
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

nebula> FETCH PROP ON player "player100", "player101", "player102", "player103" \
        YIELD properties(vertex).age AS age, properties(vertex).name AS name \
        | ORDER BY $-.age ASC, $-.name DESC;
+-------------+-----+---------------------+
| VertexID    | age | name                |
+-------------+-----+---------------------+
| "player103" | 32  | "Rudy Gay"          |
| "player102" | 33  | "LaMarcus Aldridge" |
| "player101" | 36  | "Tony Parker"       |
| "player100" | 42  | "Tim Duncan"        |
+-------------+-----+---------------------+

nebula> $var = GO FROM "player100" OVER follow \
        YIELD dst(edge) AS dst; \
        ORDER BY $var.dst DESC;
+-------------+
| dst         |
+-------------+
| "player125" |
| "player101" |
+-------------+

OpenCypher 方式语法

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

示例

nebula> MATCH (v:player) RETURN v.name AS Name, v.age AS Age  \
        ORDER BY Name DESC;
+-----------------+-----+
| Name            | Age |
+-----------------+-----+
| "Yao Ming"      | 38  |
| "Vince Carter"  | 42  |
| "Tracy McGrady" | 39  |
| "Tony Parker"   | 36  |
| "Tim Duncan"    | 42  |
+-----------------+-----+
...

# 首先以年龄排序,如果年龄相同,再以姓名排序。
nebula> MATCH (v:player) RETURN v.age AS Age, v.name AS Name  \
        ORDER BY Age DESC, Name ASC;
+-----+-------------------+
| Age | Name              |
+-----+-------------------+
| 47  | "Shaquille O'Neal" |
| 46  | "Grant Hill"      |
| 45  | "Jason Kidd"      |
| 45  | "Steve Nash"      |
+-----+-------------------+
...

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。

nebula> MATCH (v:player{name:"Tim Duncan"}) --> (v2) \
        RETURN v2.name AS Name, v2.age AS Age  \
        ORDER BY Age;
+-----------------+--------------+
| Name            | Age          |
+-----------------+--------------+
| "Tony Parker"   | 36           |
| "Manu Ginobili" | 41           |
| "Spurs"         | UNKNOWN_PROP |
+-----------------+--------------+

nebula> MATCH (v:player{name:"Tim Duncan"}) --> (v2) \
        RETURN v2.name AS Name, v2.age AS Age  \
        ORDER BY Age DESC;
+-----------------+--------------+
| Name            | Age          |
+-----------------+--------------+
| "Spurs"         | UNKNOWN_PROP |
| "Manu Ginobili" | 41           |
| "Tony Parker"   | 36           |
+-----------------+--------------+

最后更新: November 24, 2021
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