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add toSet function #1649

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Apr 13, 2022
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add toSet function #1649

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21 changes: 15 additions & 6 deletions docs-2.0/3.ngql-guide/3.data-types/9.type-conversion.md
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Original file line number Diff line number Diff line change
Expand Up @@ -2,19 +2,14 @@

类型转换是指将表达式的类型转换为另一个类型。

## 遗留兼容问题

nGQL 1.0 使用 C 语言风格的类型转换（显示或隐式）：`(type_name)expression`。例如`YIELD (int)(TRUE)`，结果为`1`。但是对于不熟悉 C 语言的用户来说，很容易出错。

从 nGQL 2.0 开始使用 openCypher 的方式进行类型强制转换。

## 类型强制转换函数

| 函数 | 说明 |
| :--- | :--- |
| toBoolean() | 将字符串转换为布尔。 |
| toFloat() | 将整数或字符串转换为浮点数。 |
| toInteger() | 将浮点或字符串转换为整数。|
| toSet() |将列表或集合转换为集合。|
| type() | 返回字符串格式的关系类型。 |

## 示例
Expand Down Expand Up @@ -76,4 +71,18 @@ nebula> MATCH (n:player) \
+-------+
| 2 |
+-------+

nebula> RETURN toSet(list[1,2,3,1,2]) AS list2set;
+-----------+
| list2set |
+-----------+
| {3, 1, 2} |
+-----------+

nebula> RETURN toSet(set{1,2,3,1,2}) AS set2set;
+-----------+
| set2set |
+-----------+
| {3, 2, 1} |
+-----------+
```