How to create and optimize indexes in MySQL?

In MySQL, you can use the CREATE INDEX statement to create an index. For example, to create an index named index_name in a table named table_name, you can use the following syntax:

CREATE INDEX index_name
ON table_name (column1, column2, ...);

To optimize the index, the following points can be taken into consideration:

1. Make sure to create indexes for commonly used queries to speed up retrieval.
2. Use the EXPLAIN statement to view the query execution plan and optimize indexes based on the query execution plan.
3. Ensure that the columns in the index are the leftmost prefixes to maximize index utilization.
4. By utilizing a covering index, which includes the indexed column in the SELECT query, it is possible to avoid accessing table data and improve query performance.
5. Avoid using functions or operators on indexed columns, as this may cause the index to become ineffective.
6. Regularly optimize the table by using the OPTIMIZE TABLE statement to improve the table structure and indexes.
7. Considering using composite indexes, combining multiple columns into one index can improve query efficiency.

Using the methods mentioned above, you can efficiently create and optimize indexes to enhance the performance and query efficiency of the database.