在编写存储过程或是触发器时,必须把查询出的结果存入于结果类型相同的变量中,上面的sql应改为 select to_char(count(*))as KNUM into 变量名称 from tdkdy t where to_char(time,'yyyy')='year' and rownum = 1 group by to_char(time,'mm') ;

select出来的结果要放到变量中去，select ... into .... from ... where ....