# UPPER

将字符串转换为大写字母。

## 语法

```
UPPER(STRING)
```

## 参数

#### STRING

类型：`string`

一个字符序列。

## 返回

类型：`string`

`STRING` 为大写字母。

***

## 示例

> SELECT UPPER("a") = "A" AND UPPER("abc") = "ABC" AND UPPER("123") = "123" AND UPPER("abc") = "ABC" AND UPPER('-=@#$') = "-=@#$" AND UPPER(null) is null AND UPPER(CAST(null as varchar)) is null

| STRING | 输出 |
| --- | --- |
| a | A |
| abc | ABC |
| 123 | 123 |
| abc | ABC |
| -=@#$ | -=@#$ |
| `null` | `null` |