字符串

Nebula Graph使用关键字string（变长）或fixed_string(<length>)（定长）声明字符串类型数据，格式为双引号或单引号包裹的任意长度的字符串，例如"Shaquille O'Neal"或'This is a single-quoted literal string'。

字符串类型

Nebula Graph支持定长字符串和变长字符串。示例如下：

  • 定长字符串

    1. nebula> CREATE TAG t1 (p1 fixed_string(10));

  • 变长字符串

    1. nebula> CREATE TAG t2 (p2 string);

转义字符

字符串中不支持直接换行，可以使用转义字符实现，例如：

  • "\n\t\r\b\f"

  • "\110ello world"

OpenCypher兼容性

openCypher、Cypher和nGQL之间有一些细微区别，例如下面openCypher的示例，不能将单引号替换为双引号。

  1. # File: Literals.feature
  2. Feature: Literals
  4. Background:
  5.     Given any graph
  6.  Scenario: Return a single-quoted string
  7.     When executing query:
  8.       """
  9.       RETURN '' AS literal
  10.       """
  11.     Then the result should be, in any order:
  12.       | literal |
  13.       | ''      |    # Note: it should return single-quotes as openCypher required.
  14.     And no side effects

Cypher的返回结果同时支持单引号和双引号，nGQL遵循Cypher的方式。

  1. nebula > YIELD '' AS quote1, "" AS quote2, "'" AS quote3, '"' AS quote4
  2. +--------+--------+--------+--------+
  3. | quote1 | quote2 | quote3 | quote4 |
  4. +--------+--------+--------+--------+
  5. | ""     | ""     | "'"    | """    |
  6. +--------+--------+--------+--------+