MySQL Indexes: Key Creation Tips

When creating an index, it is important to pay attention to the following points:

1. Choose the appropriate columns: Indexes will only bring performance improvements on columns that are frequently used as query conditions. Generally, choose primary keys, unique constraint columns, or columns used frequently as query conditions as index columns.
2. Do not over-index: having too many indexes will increase maintenance costs and will decrease performance when inserting, updating, and deleting data. Therefore, only create necessary indexes.
3. Consider using a composite index: If you frequently need to query multiple columns at the same time, consider creating a composite index. This type of index can improve the performance of queries involving multiple columns, but it also comes with additional maintenance costs.
4. Prefix indexing can be used for longer string columns to reduce the size of the index and improve query performance.
5. Pay attention to the order of indexes: For a compound index, the order of index columns is very important. Querying based on the order of index columns will fully utilize the index.
6. Avoid using indexed columns for calculations: If indexed columns are used for calculations in the query conditions, the index will not be used, impacting query performance. It is best to avoid calculating indexed columns in query conditions as much as possible.
7. Regular maintenance of indexes: as data grows and changes, the performance of indexes may decrease. Performing regular index reorganization and rebuilding can help maintain high performance of the indexes.
8. Pay attention to the selectivity of indexes: The selectivity of an index refers to the proportion of unique values in the index column. The higher the selectivity, the better the performance of the index. Therefore, columns with higher selectivity should be chosen as index columns.
9. Consider using full-text index: For columns containing a large amount of text, such as article content, consider using a full-text index to improve the performance of keyword searches.

In conclusion, when creating an index, it is necessary to choose and balance based on specific business needs and data characteristics in order to improve query performance.