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dbms_random

原创 Linux操作系统 作者:perfychi 时间:2012-07-20 11:12:08 0 删除 编辑
SQL> select text from all_source where name=upper('dbms_random') and type='PACKAGE';
PACKAGE dbms_random AS

    ------------
    --  OVERVIEW
    --
    --  This package should be installed as SYS.  It generates a sequence of
    --  random 38-digit Oracle numbers.  The expected length of the sequence
    --  is about power(10,28), which is hopefully long enough.
    --
    --------
    --  USAGE
    --
    --  This is a random number generator.  Do not use for cryptography.
    --  For more options the cryptographic toolkit should be used.
    --
    --  By default, the package is initialized with the current user
    --  name, current time down to the second, and the current session.
    --
    --  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.
    --
    --------
    --  EXAMPLES
    --
    --  To initialize or reset the generator, call the seed procedure as in:
    --      execute dbms_random.seed(12345678);
    --    or
    --      execute dbms_random.seed(TO_CHAR(SYSDATE,'MM-DD-YYYY HH24:MI:SS'));
    --  To get the random number, simply call the function, e.g.
    --      my_random_number BINARY_INTEGER;
    --      my_random_number := dbms_random.random;
    --    or
    --      my_random_real NUMBER;
    --      my_random_real := dbms_random.value;
    --  To use in SQL statements:
    --      select dbms_random.value from dual;
    --      insert into a values (dbms_random.value);
    --      variable x NUMBER;
    --      execute :x := dbms_random.value;
    --      update a set a2=a2+1 where a1 < :x;

    -- Seed with a binary integer
    PROCEDURE seed(val IN BINARY_INTEGER);
    PRAGMA restrict_references (seed, WNDS);

    -- Seed with a string (up to length 2000)
    PROCEDURE seed(val IN VARCHAR2);
    PRAGMA restrict_references (seed, WNDS);

    -- Get a random 38-digit precision number, 0.0 <= value < 1.0
    FUNCTION value RETURN NUMBER;
    PRAGMA restrict_references (value, WNDS);

    -- get a random Oracle number x, low <= x < high
    FUNCTION value (low IN NUMBER, high IN NUMBER) RETURN NUMBER;
    PRAGMA restrict_references (value, WNDS);

    -- get a random number from a normal distribution
    FUNCTION normal RETURN NUMBER;
    PRAGMA restrict_references (normal, WNDS);

    -- get a random string
    FUNCTION string (opt char, len NUMBER)
          /* "opt" specifies that the returned string may contain:
             '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
          */
        RETURN VARCHAR2;  -- string of characters
    PRAGMA restrict_references (string, WNDS);

    -- Obsolete, just calls seed(val)
    PROCEDURE initialize(val IN BINARY_INTEGER);
    PRAGMA restrict_references (initialize, WNDS);

    -- Obsolete, get integer in ( -power(2,31) <= random < power(2,31) )
    FUNCTION random RETURN BINARY_INTEGER;
    PRAGMA restrict_references (random, WNDS);

    -- Obsolete, does nothing
    PROCEDURE terminate;

    TYPE num_array IS TABLE OF NUMBER INDEX BY BINARY_INTEGER;
END dbms_random;

86 rows selected.

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