Convert decimal to hexadecimal

Create Function DBO. f_dec_hex (@ num bigint, @ length INT)
Returns varchar (16)
As
Begin
-- Author: pbsql
-- @ Num is the positive integer to be converted to a hexadecimal string. If it is a negative number, '0' is returned'
-- @ Length indicates the length of the hexadecimal string to be returned.
-- If @ length is negative, '0' is returned. If it is 0, a hexadecimal string of the actual length is returned.
-- If @ length is greater than 0, return the hexadecimal string with the length of @ length (from the low position, the BITs do not fill in '0' when the BITs do not exceed the bits, and the bits are truncated when the BITs do not exceed the bits)
Declare @ result varchar (16)
Set @ result =''
If @ num <= 0 or @ length <0
Set @ result = '0'
Else
Begin
While @ num <> 0
Select @ result = substring ('0123456789abcdef ', @ num % 16 + 1, 1) + @ result, @ num = @ num/16
If @ length> 0
Set @ result = right (replicate ('0', @ length) + @ result, @ length)
End
Return @ result
End
Go