MySQL Composite Index Best Practices

Consider the following points when creating a composite index:

1. A composite index includes multiple fields, and the order of the fields can impact query performance. Typically, placing the most frequently used fields for queries at the front of the index can improve query efficiency.
2. The fields’ order in a composite index should match the order of fields in the query, otherwise the index will not be effectively utilized.
3. The number of fields in a composite index should be moderate, as having too many fields will increase the maintenance cost and space occupancy of the index, while also reducing its efficiency.
4. When selecting a composite index, consider the frequency of queries and performance requirements, and try to choose fields that are frequently used in queries.
5. For composite indexes, it is preferable to use simpler field types in order to enhance index efficiency, avoiding lengthy string indexes or complex data types.
6. It is important to ensure the consistency of data types for index fields when creating a composite index, as it can impact the performance of the index.
7. Updating composite indexes can affect performance, so it is important to consider the selection and optimization of indexes when performing a large number of insertions, updates, or deletions on a table.
8. Regularly optimizing and maintaining the unified index can improve query performance and reduce the burden on the database.