來源為 https://www.slideshare.net/billkarwin/how-to-design-indexes-really
個人隨手筆記
檢測哪一些存取(query)是慢的
SET GLOBAL slow_query_log = ON;
First Star: Rows referenced by your query are grouped together in the index.
Second Star: Rows referenced by your query are ordered in the index the way you want them.
Third Star: The index contains all columns referenced by your query.