MySQL 8 Administrator???s Guide

Uses of indexes in MySQL 8

Indexes are mainly used to find a row of specific values without iterating a complete table. If an index is not define,d then MySQL 8 will start searching from the first row and then read the entire table, which makes for a costly operation. MySQL 8 uses indexes for the following operations:

• To sort or group tables when it is done on the left-most prefix of an index. This means that if all keys are defined for the DESC clause, then the keys will be considered in reverse order, and if all keys are followed by ASC, then the keys will be considered in forward order.
• To find rows whose values match with the WHERE clause.
• In the case of multiple column indexes, any left-most prefix of the index can be used to find the ...