1 votes 1 votes A relation schema for a bus reservation is given below. Bus(BusNo, Bname, travel-agent) Passenger (Pid,pname,age) Reservation (Pid,class,travel-Agent) Databases sql databases query + – Mk Utkarsh asked Jan 23, 2018 Mk Utkarsh 746 views answer comment Share Follow See all 4 Comments See all 4 4 Comments reply Anu007 commented Jan 23, 2018 reply Follow Share None of these 1 votes 1 votes Mk Utkarsh commented Jan 23, 2018 reply Follow Share how EXIST react to empty set? 0 votes 0 votes Anu007 commented Jan 23, 2018 reply Follow Share Exist on empty retuen false i.e. does not select that record. 3 votes 3 votes joshi_nitish commented Jan 23, 2018 reply Follow Share there is also syntax error in last line Pid=(select Pid from passengers where age=30), in place of '=' there should be 'IN' 0 votes 0 votes Please log in or register to add a comment.