### SIN

#### Description
The sine function (SIN) is a mathematical function used to calculate the sine value of a given angle. In SQL language, we can use the `sin` function to achieve this functionality. This function accepts one parameter and returns a value of type `double`.

#### Syntax
```
sin(expr)
```
#### Parameters
- `expr`: A `double` type value representing the angle for which the sine value needs to be calculated.

#### Return Value
Returns a `double` type value representing the sine value of the given angle.

#### Example Usage

1. Calculate the sine value of 0 radians:
```sql
SELECT sin(0);
```
Results:
```
0.0
```
2. Calculate the sine value of π/2 radians (i.e., 90 degrees):
```sql
SELECT sin(pi()/2);
```
Results:
```
1.0
```
3. Calculate the sine of π radians (i.e., 180 degrees):
```sql
SELECT sin(pi());
```
Results:
```
1.2246467991473532E-16
```
4. Calculate the sine value of 3π/2 radians (i.e., 270 degrees):
```sql
SELECT sin(3 * pi()/2);
```
Results:
```
-1.0
```
5. Calculate the sine value of a negative angle (-π/4 radians, i.e., -45 degrees):
```sql
SELECT sin(-pi()/4);
```
Results:
```
-0.7071067811865475
```
#### Precautions
- Ensure that the input parameter is a valid numerical value, otherwise it may lead to incorrect calculation results.
- When the input angle value is negative, the sine function will return the corresponding negative value.
- The sine function can be used in practical applications to solve trigonometric problems, vibrations, and wave issues.