How can the speed of querying with a combined index in MySQL be improved?

To improve the speed of MySQL queries using composite indexes, you can consider the following aspects: 1. Optimize the query statement: Ensure that the conditions, sorting, and grouping fields in the query statement are in the same order as the composite index, so MySQL can use the composite index as efficiently as possible. 2. Reduce the number of index fields: Only include necessary fields in the composite index, as having too many index fields can increase the index size and update costs, decreasing query performance. 3. Use covering index queries: If the queried fields are all included in the composite index, MySQL can directly read data from the index without having to search for data rows, improving query performance. 4. Optimize the selectivity of the index: Selectivity refers to the ratio of the number of different values in the index to the total number of data rows. Higher selectivity indicates better index differentiation and improved query performance. You can enhance the selectivity of the index through optimizing data types, adding statistics, etc. 5. Monitor and optimize index performance: Use MySQL performance monitoring tools like Explain and Slow Query Log to monitor query performance and optimize indexes based on the execution plan. 6. Regular maintenance and re-optimization of indexes: Depending on the frequency of database insert, delete, and update operations, regularly re-optimize and maintain indexes by deleting unnecessary indexes, rebuilding indexes, defragmenting, etc., to maintain index efficiency. 7. Use appropriate storage engines: MySQL supports various storage engines, each with different ways of handling indexes and performance. Choosing the right storage engine can improve query performance. 8. Control the size of the query result set: Try to limit the amount of data returned by queries using LIMIT, etc., to reduce unnecessary network transmission and memory consumption. In conclusion, by optimizing query statements, reducing the number of index fields, using covering index queries, optimizing selectivity of indexes, monitoring and optimizing index performance, regular maintenance and re-optimization of indexes, using appropriate storage engines, and controlling the size of the query result set, you can improve the speed of MySQL queries using composite indexes.