The information below i get from http://dev.mysql.com/doc/refman/8.0/en/optimize-overview.html
Optimization at the database level
Database performance depends on several factors at the database level, such as tables, queries, and configuration settings.
1. Are the tables structured properly?
2. In particular, do the columns have the right data types, and does each table have the appropriate columns for the type of work?
3. Are the right indexes in place to make queries efficient?
4. Are you using the appropriate storage engine for each table?
5. Does the application use an appropriate locking strategy?
6. Are all memory areas used for caching sized correctly?
System bottlenecks typically arise from these sources
1. Disk seeks. It takes time for the disk to find a piece of data
2. Disk reading and writing
3. CPU cycle
4. Memory bandwidth
原文：http://www.cnblogs.com/mengjianzhou/p/5939572.html