ON City.Country=Country.Code AND City.Population > 5000000
WHERE Country.Name LIKE 'C%' AND Country.Population > 10000000;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE Country range Name Name 52 NULL 17 Using index condition; Using where; Using MRR
1 SIMPLE City hash_range Population,Country #hash#Country:Population 3:4 world.Country.Code 31 Using where; Using MRR; Using join buffer (flat, BNLH join)
1 SIMPLE Country range Name Name 52 NULL # Using index condition; Using where; Using MRR
1 SIMPLE City hash_range Population,Country #hash#Country:Population 3:4 world.Country.Code # Using where; Using MRR; Using join buffer (flat, BNLH join)