On Friday 26 October 2001 10:00, Dana Holt wrote:
> Can I automatically generate a random, unique, integer value in a certain
> range when inserting data into a column using SQL?
>
> If so, how?
Random is easy. Just find a good RNG (random number generator) somewhere
(there are many available on the 'net, search on Google). Or, use the RAND
function that comes with MySQL. You can find RNGs that have extremely long
periods.
Unique is easy. Just use an auto-increment field in MySQL.
Random _and_ unique are not that simple.
Grab a handy book on cryptography. There are operations on numeric
(bitstring) values that will do what you want starting with a guaranteed
unique input (such as from an auto-increment field or a sequence). The key
thing to remember is that uniqueness and randomness can be derived in two
steps, they need not be done in one.
Are you sure it needs to be "random"? By definition, if it is unique, it
can't be totally random since a random number would have a certain
probability of being the same value twice after a certain number of samples.
Is there a simple SQL statement that will do what you want? Probably not.
Best,
Kyle
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