存储过程中如何产生随机数？

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      存储过程中如何产生随机数？

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3. 4.8.8 How do I generate random numbers in SPL?
   
4. On 8th Dec 1997 [email]johnl@informix.com[/email] (Jonathan Leffler) wrote:-
   
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6. Since that's the case, we need a proper random number generator. On the assumption that the C Standard committee knew roughly what they were doing when they specified a random number generator in the ISO 9899:1990 standard, here's an implementation of that generator in two functions, sp_setseed(0 and sp_random(). The range of returned values is 0..32767. Note the comment about MOD. That was in a 9.12.UC2 IUS system.
   
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8. -- @(#)$Id: ifaq04c.htm,v 1.11 1999/01/09 14:30:06 root Exp $ -- -- Simple emulation of SRAND and RAND in SPL -- Using random number generator suggested by C standard (ISO 9899:1990)
   
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11. CREATE PROCEDURE sp_setseed(n INTEGER)
    
12.         DEFINE GLOBAL seed DECIMAL(10) DEFAULT 1;
    
13.         LET seed = n;
    
14. END PROCEDURE;
    
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16. CREATE PROCEDURE sp_random() RETURNING INTEGER;
    
17.         DEFINE GLOBAL seed DECIMAL(10) DEFAULT 1;
    
18.         DEFINE d DECIMAL(20,0);
    
19.         LET d = (seed * 1103515245) + 12345;
    
20.         -- MOD function does not handle 20-digit values...  Dammit!!
    
21.         LET seed = d - 4294967296 * TRUNC(d / 4294967296);
    
22.         RETURN MOD(TRUNC(seed / 65536), 32768);
    
23. END PROCEDURE;
    

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