这句话结构是什么,是什么从句?They have no idea at all where he has gone同位语

英语中引导同位语从句的词通有连词 that,whether,连接副词 how,when,where等.（注：if,which 不能引导同位语从句.）如：
l have no idea when he will be back．我不知道他什么时候回来.
He must answer the question whether he agrees to it or not.
他必须回答他是否同意这样一个问题.
四、有时同位语从句可以不紧跟在说明的名词后面,而被别的词隔开.如：
Several years later,word came that Napoleon himself was coming to inspect them．
几年以后,有消息传来说拿破仑要亲自视 察他们.
The thought came to him that maybe the enemy had fled the city．
他突然想起可能敌人已经逃出城了.

这是同位语从句
idea和后面的where引导的句子互为同位语

是同位语从句.
英语中引导同位语从句的词通有连词 that，whether，连接副词 how,when,where等。（注：if,which 不能引导同位语从句。）如:
I have no idea when he will be back．我不知道他什么时候回来。
He must answer the question whether he agrees to if o...