Write three functions in SQL that do the following: 1. The first function takes any integer and converts it into a hexadecimal number. It could also take the hexadecimal number and convert it back to an integer.

2. The second function takes an integer and converts it into an octal number. It could also take the octal number and convert it to an integer.

3. The third function takes an integer and converts it into a binary number. It could also take the binary number and convert it to an the integer.