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¶
ngql
<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¶
```ngql 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; +-----+---------------------+ | age | name | +-----+---------------------+ | 32 | "Rudy Gay" | | 33 | "LaMarcus Aldridge" | | 36 | "Tony Parker" | | 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¶
ngql
<RETURN clause>
ORDER BY <expression> [ASC | DESC] [, <expression> [ASC | DESC] ...];
示例¶
```ngql nebula> MATCH (v:player) RETURN v.player.name AS Name, v.player.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.player.age AS Age, v.player.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。
```ngql nebula> MATCH (v:player{name:"Tim Duncan"}) --> (v2) \ RETURN v2.player.name AS Name, v2.player.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.player.name AS Name, v2.player.age AS Age \ ORDER BY Age DESC; +-----------------+--------------+ | Name | Age | +-----------------+--------------+ | "Spurs" | UNKNOWN_PROP | | "Manu Ginobili" | 41 | | "Tony Parker" | 36 | +-----------------+--------------+ ```