Due to the fields in the fields of "gender", the variation value in the field is rare, and the establishment of different NORMAL index is useless. However, in the query, the search "Gender is male than 30 years old" in the query, if it does not adex, it will be very slow when the data is increased, in fact, Oracle is a solution in Oracle. , That is, the Bitmap type index, I experimentally found that the speed can be greatly improved after adding this type of index.
