请创建一个长度为10的字符串，由大写字母、小写字母和数字随机组成，不能有重复的字符。
Here is a possible solution:

```python
import random
import string

# Define the set of characters to choose from
characters = string.ascii_letters + string.digits

# Generate a random string of length 10 without duplicates
result = ''.join(random.sample(characters, k=10))

print(result)
``` 

Output: 
```
9FyDpGq3hW
```