1. The establishment of the business scene index corresponding combination, generally in the primary key, foreign key, used to filter the query field, in accordance with a combination of the closeness between the field, certain order index.
For example: indexing t_org_exam_join_member_day.
First consider the combination between the query field. Therefore first establish a composite index:
假如 A = f_organization_id, B = f_day, C = f_member_id
Then the combined effect is that from A, A and B, A and B, and C