**Description**: The value that matches the specified timestamp range is returned, if existing; or an interpolation value is returned.
**Description**: The value that matches the specified timestamp range is returned, if existing; or an interpolation value is returned. The value of `ignore_null_values` can be 0 or 1, 1 means null values are ignored. The default value of this parameter is 0.
**Return value type**: Same as the column being operated upon