Random string generator

BEGIN
/*
To initialize or reset the generator, 
call the seed procedure. Seed with a 
binary integer
*/
dbms_random.seed(1234535678);

/*
Get a random 38-digit precision 
number, 0.0 <= value < 1.0
*/
dbms_output.put_line(
    TO_CHAR(dbms_random.value)
    );

/*
get a random real number between 1 and 5
*/
dbms_output.put_line(
    TO_CHAR(dbms_random.VALUE(1,5))
    );

/*
get a random integer between 1 and 100
*/
dbms_output.put_line(
    TO_CHAR(TRUNC(dbms_random.VALUE(1,100)))
    );

/*
get a random string.
First parameter:
'u','U' : upper case alpha characters only
'l','L' : lower case alpha characters only
'a','A' : alpha characters only (mixed case)
'x','X' : any alpha-numeric characters (upper)
'p','P' : any printable characters
Second Parameter: Length (max 60)
*/
dbms_output.put_line(
    dbms_random.string('p',8)
    );

/*
Seed with a string (up to length 2000)
*/
dbms_random.seed(
    TO_CHAR(SYSDATE,'MM-DD-YYYY HH24:MI:SS')
    );

/*
get a random integer between 1 and 100
*/
dbms_output.put_line(
    TO_CHAR(TRUNC(dbms_random.VALUE(1,100)))
    );

END;

Reader's Comments

1. Robert Vollman | 29 Jul 2005 8:47 am

   Speaking of random numbers, what do you think about this problem of mine:

   http://thinkoracle.blogspot.com/2005/05/random-numbers.html

2. Eddie | 29 Jul 2005 11:38 am

   Robert, I could not understand your problem. However, here are some clarifications about the package DBMS_RANDOM which I’m sure you already know, but does not hurt to add them here for future reference:

   The package DBMS_RANDOM is only available in Oracle version 8 and above.

   If you want to encrypt sensitive data, then you should use the built-in package DBMS_OBFUSCATION_TOOLKIT, not DBMS_RANDOM .

   For an analysis of DBMS_RANDOM, how it works and the quality of the generated random numbers or strings, I suggest this article.

   The following functions are not documented in Oracle 8i and Oracle 9i DBMS_RANDOM‘s documentation, but they are in Oracle 10g‘s: NORMAL, VALUE and STRING. A look at the source code of DBMS_RANDOM reveals these hidden and useful functions.

3. edcas | 21 Nov 2005 11:50 pm

   Hi Eddie,

   I can’t really figure out what’s the use for SEED procedure here. Can you explain further?

   As I execute the code below, it give me the same result.

   BEGIN
   dbms_random.seed(1234535678);
   dbms_output.put_line('Random1: '||dbms_random.value);
   END;
   
   Random1: .62004818671882084550610341425311827476
   

4. Eddie Awad | 22 Nov 2005 12:52 pm

   edcas, the seed is needed to generate the random number or string. The seed can be a number or a string. If you do not initialize the generator by explicitly calling the seed procedure, a default seed is used, in that case, it is equal to:

   TO_CHAR(SYSDATE,'MM-DD-YYYY HH24:MI:SS') ||
   USER || USERENV('SESSIONID')
   

   So, if you do not seed, and then call dbms_random.value, chances are you will not get the same random value.

   The dbms_random package specification says: If this package is seeded twice with the same seed, then accessed in the same way, it will produce the same results in both cases.

   So, your observation is correct, given the same seed over and over again, you will get the same result each time you execute the same dbms_random procedure.

   How can a seed be used? well, one example is when you want to generate a random password. You would seed the generator with the username, so distinct usernames will have distinct random passwords, but same usernames will have the same random password since the seed (username) is the same.