MYSQL performance

https://www.mysql.com/why-mysql/performance/

https://www.slideshare.net/oysteing/how-to-analyze-and-tune-mysql-queries-for-better-performance-75441170

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

https://www.slideshare.net/jynus/query-optimization-with-mysql-57-and-mariadb-10-even-newer-tricks?next_slideshow=1

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/