What is the customer id of the customer with the most accounts, and how many accounts does this person have?
return customer ;return accounts  ;return number of  #2 for each  #1 ;return #1 where #3 is  highest ;return id of  #4 ;return highest of  #3 ;return #5 ,  #6
['select', 'select', 'group', 'superlative', 'project', 'aggregate', 'union']