return me the number of the journals, which have more than 60 papers containing keyword " Relational Database " . 
return journals ;return papers in #1 ;return #2 that  contain the  keyword Relational Database ;return the  number of  #3 for each #1 ;return #1 where #4 is  more than  60 ;return the  number of  #5
['select', 'project', 'filter', 'group', 'comparative', 'aggregate']