Because the index is an ordered data structure, the B+Tree tree index is arranged in an orderly manner, and the leaf nodes are arranged in order from left to right. If %like is like this, I don't know which one is at the beginning. To perform a full table scan, it is easy to understand
Practice is the truth
Create an index on the field and then query
So you can see it, no index is used
There is a situation where an index will be used, the searched field, if it is an index column, index coverage will occur, and the index will also be used
Also, if you don’t understand, just remember and avoid this situation.
Lord Li
Sister Aihui Aihui
March 4, 2021