MySQL Query optimization

Assume that the database has three indexed fields, such as

1. Database fields

2. Index Field

The leftmost index is " primary key index " and the other two columns are " normal index "

3. Here are the query cases where different indexed field combinations

where leftmost index field

Select *  from where = 1

Where leftmost and intermediate index fields

Select *  from where = 1  and = 1

where three index fields

Select *  from where = 1  and = 1  and = 1

where intermediate index fields

Select *  from where = 1

where rightmost index field

Select *  from where = 1

Where after two indexed fields

Select *  from where = 1  and = 1

For more optimizations please refer to

Millions database optimization scheme of database SQL optimization Summary

MySQL Query optimization