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docs/cn/sql-reference/00-sql-reference/42-lambda-expressions.md
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title: Lambda 表达式 | ||
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Lambda 表达式是匿名函数,允许您封装逻辑并将其作为参数传递给高阶函数,例如用于处理数组、列表或其他复杂数据类型的函数。它通常接受一组输入参数和一个代码体,该代码体对集合中的每个元素或排序逻辑中的每次比较执行。 | ||
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## 语法 | ||
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```sql | ||
-- 接受一个参数 | ||
<parameter> -> <expression> | ||
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-- 接受多个参数 | ||
(<parameter1>, <parameter2>, ...) -> <expression> | ||
``` | ||
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| 参数 | 描述 | | ||
|-----------------------------------|----------------------------------------------------------------------------------------------| | ||
| `<parameter1>, <parameter2>, ...` | Lambda 将操作的值(例如,数组的元素)。 | | ||
| `->` | 将输入参数与逻辑分隔开。 | | ||
| `<expression>` | 应用于输入参数的逻辑,通常写成条件或计算。 | | ||
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## 示例 | ||
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这个 Lambda 表达式接受一个参数 n 并将 5 加到它上面: | ||
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```bash | ||
n -> (n + 5) | ||
``` | ||
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这个 Lambda 表达式接受一个整数 x,如果 x 大于 0,则返回 `Positive`,否则返回 `Non-Positive`: | ||
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```bash | ||
x -> (CASE WHEN x > 0 THEN 'Positive' ELSE 'Non-Positive' END) | ||
``` | ||
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这个 Lambda 表达式检查 num 是否为偶数。对于偶数返回 `true`,对于奇数返回 `false`: | ||
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```bash | ||
num -> (num % 2 = 0) | ||
``` | ||
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这个 Lambda 表达式将两个参数 x 和 y 相加: | ||
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```bash | ||
(x, y) -> (x + y) | ||
``` |