Oracle随机函数―dbms_random

Oracle随机函数―dbms_random
1.基础认识
关于这些函数及DBMS_RANDOM包的文件都包含在SQLPlus中： select text from all_source where name = 'DBMS_RANDOM'
and type = 'PACKAGE' order by line;
◆ TYPE num_array ◆ PROCEDURE terminate ◆ PROCEDURE seed
◆ PROCEDURE initialize ◆ FUNCTION random
◆ FUNCTION value RETURN NUMBER;
◆ FUNCTION value (low IN NUMBER, high IN NUMBER) RETURN NUMBER; ◆ FUNCTION normal RETURN NUMBER;
◆ FUNCTION string (opt char, len NUMBER) RETURN VARCHAR2;
2.应用举例
SELECT DBMS_RANDOM.RANDOM FROM DUAL;
再进一步的要求，比如，产生一个0－100的随机数，稍微变通一下就可以了：
select abs(mod(dbms_random.random,100)) from dual
3.进阶说明
dbms_random又有新函数了可以实现这些功能 FUNCTION value RETURN NUMBER;
FUNCTION value (low IN NUMBER, high IN NUMBER) RETURN NUMBER; FUNCTION normal RETURN NUMBER;
FUNCTION string (opt char, len NUMBER) RETURN VARCHAR2;
产生N到M之间的随机数
SELECT DBMS_RANDOM.VALUE(N,M) FROM DUAL;
缺省DBMS_RANDOM.VALUE返回0到1之间的随机数
SQL> select dbms_random.value, dbms_random.value(55,100) from dual; VALUE DBMS_RANDOM.VALUE(55,100) --------------- -----------------------------