分数转小数在plsql里面可以直接转换的

即可用select 1/2 from dual;得到 0.5;

小数转换分数,我自己写了一个sql语句进行实现;

select decode(mod(a, b),
              0,
              to_char(a / b),
              to_char(a / ys) || '/' || to_char(b / ys)) as result,
       ys
  from (select a, b, max(le) as ys
          from (select a, b, level as le, mod(a, level) aa, mod(b, level) bb
                  from (select s * power(10,
                                         (length((to_char(s))) -
                                         instr(to_char(s), '.'))) as a,
                               power(10,
                                     (length((to_char(s))) -
                                     instr(to_char(s), '.'))) as b
                          from (select 5.123 as s from dual))
                connect by level <= a) t
         where aa = 0
           and bb = 0
         group by a, b)

但是这句sql有个毛病，就是 小数后面的数字不能太长，否则执行时间过长，效率低下；即5.123 换成5.1212121212121的话估计会死掉；呵呵

请哪位大侠指导指导~~~~~~~