### ACOSH 
#### Description
The `ACOSH` function is used to calculate the inverse hyperbolic cosine of a given value. This function accepts a `DOUBLE` type parameter and returns a `DOUBLE` type numerical result.

#### Syntax
```
ACOSH(expr)
```
#### Parameters
- `expr`: The `DOUBLE` type value for which the inverse hyperbolic cosine needs to be calculated.

#### Return Value
Returns the inverse hyperbolic cosine of the parameter `expr`, with the result type being `DOUBLE`.

#### Example Usage
1. Calculate the inverse hyperbolic cosine of `2`:
```
SELECT ACOSH(2); -- The result is approximately 1.3169578969248166
```
2. Calculate the inverse hyperbolic cosine of `1` (the result is `0`, because `1` is the minimum value for the `ACOSH` function):
```
SELECT ACOSH(1); -- The result is 0.0
```
3. Calculate the inverse hyperbolic cosine of a decimal value close to `0`:
```
SELECT ACOSH(0.0001); -- Result is approximately NaN
```
4. Calculate the inverse hyperbolic cosine of a negative number (result is `NaN` because the `ACOSH` function only accepts positive number arguments):
```
SELECT ACOSH(-1); -- The result is NaN
```
5. Calculate the inverse hyperbolic cosine of multiple values in a query:
```
SELECT ACOSH(2.5), ACOSH(3.7), ACOSH(0.5); -- The results are approximately 1.566799236972411, 1.9826969446812033, and NaN respectively
```
#### Notes
- The `ACOSH` function only accepts positive number parameters. If a negative number or zero is passed, it will return `NaN` (Not a Number).
- When the parameter value is close to `0`, the inverse hyperbolic cosine value becomes very large. In practical applications, attention should be paid to the issue of numerical overflow.
- The `ACOSH` function and the `COSH` function are inverse operations of each other. The `COSH` function is used to calculate the hyperbolic cosine value, while the `ACOSH` function is used to calculate its inverse operation result.