From the navigation bar, we notice that Google uses hexadecimal values to identify records:
print above has been removed from GMail, but the same is true for other services like Google Drive.
What is the advantage of using hexadecimal values instead of integers?
Hexadecimal is a slightly shorter representation. For example, the following two values are identical:
999999999 DEX
3B9AC9FF HEX
You also have a better view of the bit distribution, since each position in hexadecimal equals 4 bits:
3 B 9 A C 9 F F HEX
0011 1011 1001 1010 1100 1001 1111 1111 BIN
What kind of column is appropriate in this case: string (varchar), binary, other
Usually numeric, but can be binary. Hexa is just a representation; is the case of the GUID type, which SQL Server stores as a varbinary(16) .
For an example of this type of conversion, see this answer in Stack Overflow: link