MySQL 8 allows you to create an index on a single column, as well as on multiple columns. The maximum number of indexes per table and maximum index length depend on the storage engine. Mostly, all the storage engines allow at least 16 indexes per table and total index lengths of at least 256 bytes, but most of the storage engines permit higher limits.
Column-level indexing
Column indexes
This is the most common way to define an index where only a single column is involved. MySQL 8 stores a copy of column values in a data structure so that rows can be accessed quickly. MySQL 8 uses a B-Tree data structure to enable values to be accessed quickly. The B-Tree execution will work based on operators, such as =, <, >, BETWEEN...
