Question

I’m looking for the best way to basically get a unique number (guaranteed, not some random string or current time in milliseconds & of a reasonable length about 8 characters) using MySQL (or other ways suggestions welcome).

I just basically want to run some SELECT ... statement and have it always return a unique number with out any inserting into database. Just something that increments some stored value and returns the value and can handle a lot of requests concurrently, without heavy blocking of the application.

I know that I can make something with combinations of random numbers with higher bases (for shorter length), that could make it very unlikely that they overlap, but won’t guarantee it.

It just feels like there should be some easy way to get this.

To clarify…

I need this number to be short as it will be part of a URL and it is ok for the query to lock a row for a short period of time. What I was looking for is maybe some command that underhood does something like this …

LOCK VALUE
RETURN VALUE++
UNLOCK VALUE

Where the VALUE is stored in the database, a MySQL database maybe.

Answer 1

You seek UUID().

http://dev.mysql.com/doc/refman/5.0/en/miscellaneous-functions.html#function_uuid

mysql> SELECT UUID();
    -> '6ccd780c-baba-1026-9564-0040f4311e29'

It will return a 128-bit hexadecimal number. You can munge as necessary.