https://www.mysql.com/why-mysql/performance/
https://www.slideshare.net/oysteing/how-to-analyze-and-tune-sql-queries-for-better-performance
https://www.slideshare.net/oysteing/using-optimizer-hints-to-improve-mysql-query-performance
http://www.unofficialmysqlguide.com/cost-based-optimization.html
https://dev.mysql.com/doc/refman/5.7/en/cost-model.html
https://dev.mysql.com/doc/refman/5.7/en/internal-temporary-tables.html
https://dev.mysql.com/doc/refman/5.7/en/innodb-persistent-stats.html
http://www.unofficialmysqlguide.com/cost-based-optimization.html
https://stackoverflow.com/questions/44334508/how-number-of-items-in-in-clause-relates-to-index-usage
https://mydbops.wordpress.com/2016/09/26/cost-based-optimization-in-mysql-5-7/