Show the carriers that have both phones with memory smaller than 32 and phones with memory bigger than 64.
SELECT Carrier FROM phone WHERE Memory_in_G  <  32 INTERSECT SELECT Carrier FROM phone WHERE Memory_in_G  >  64
phones with memory smaller than 32 refers to Memory_in_G < 32; phones with memory bigger than 64 refers to Memory_in_G > 64; both conditions met by the same carrier refers to use of INTERSECT in SQL;