我的sql语句select * from table where 1=1(${if(len(a)==0,"","and num >= '"+a+"'")}${if(len(b)==0,"","and num <= '"+b+"'")})(${if(len(c)==0,"","and count >= '"+c+"'")}${if(len(d)==0,"","and count >= '"+d+"'")})and name = '${name}' and zhiwu = '${zhiwu}'我这样加括号就是语法错误。想实现的功能是1.当a、b两个参数有值时,num取在a、b两个数之前的数据;2.当c、d两个参数有值时,count取在c、d两个数之前的数据;3.当a、b、c、d都有值时,把1、2两个条件用or连接sql应该怎么写,求教!!!