From Longman Dictionary of Contemporary Englishhave/know all the answershave/know all the answersinformal to be very sure that you know everything about a situation, especially when you do not He acts like he has all the answers. → answer
Examples from the Corpus
have/know all the answers• He was a modest and unassuming man who never gave the impression that he knew all the answers.• In the current situation many issues as yet remain unresolved and we do not have all the answers.• But I don't have all the answers.• Will that have all the answers?• Anyone can claim to have all the answers.• We are supposed to have all the answers. 