SQL Index Creation: Best Practices Guide

Several important factors need to be considered when creating an index.

1. Indexes should be created based on actual query needs, neither too many nor too few. Having too many indexes will increase the time for insertions, updates, and deletions, while too few indexes will negatively affect query performance.
2. Ensure that indexes are created for columns frequently used in search conditions, such as primary keys, foreign keys, and columns used for sorting and filtering.
3. Avoid creating indexes for columns with a high number of sparse and repetitive values, as they do not perform well.
4. It is generally recommended to place columns with high selectivity at the front of an index in order to improve its efficiency.
5. When dealing with composite indexes, it is important to determine the order and combination of columns based on the actual query requirements.
6. Given the size and amount of data in a table, it is crucial to carefully select indexes for large tables and tables with a large amount of data.
7. Regularly review the usage of indexes, adjust and optimize them in a timely manner to avoid performance issues caused by having too many or too few indexes.