Automatically provide unique id in the database

Question

In my project i need to register a donor and I need the user to enter his information and the system registers him and generate a unique id to the donor.

Answer 1

If the donor id has to be used outside mysql, consider the additional usage of UUID() -- http://dev.mysql.com/doc/refman/5.0/en/miscellaneous-functions.html#function_uuid (in addition to the integer primary key that is); external interfaces won't be as vulnerable to parameter-playing (e.g. "let's see if I cant't get the data for donor 'my-id + 1'") if the exposed id is a uuid.

That said, as mentioned in the mysql docs, if you need the uuids to be unpredictable, don't use the UUID()-Function but use e.g. an hash-algorithm (e.g. sha1 ) over the users data and sufficient entropy from the system (urandom, ...)

Edit: Have a read at wikipedia http://en.wikipedia.org/wiki/Universally_unique_identifier on how to build format a uuid.

Answer 2

Make a table with a field ID that has an index and has auto increment on.

CREATE TABLE Persons
(
ID int NOT NULL AUTO_INCREMENT,
LastName varchar(255) NOT NULL,
FirstName varchar(255),
Address varchar(255),
City varchar(255),
PRIMARY KEY (ID)
)

If you now add a new rule with MySQL you can leave the ID field empty, or just don't pass it like below

INSERT INTO Persons(LastName, FirstName, Address, City) VALUES('Your firstname','lastname','adress','city')

Answer 3

Use auto-incremented integer field. Or use an auto-generated GUID. (Both of these work in T-SQL, I did not try MySQL.)