因为是数据库的移值，导致表中double中的值有的为null，怎么一次性更新表中double类型的null值为0.0？？

update tname
set r1=nvl(r1,0.0),r2=nvl(r2,0.0),r3=nvl(r3,0.0),r4=nvl(r4,0.0),r5=nvl(r5,0.0),r6=nvl(r6,0.0);