Description: A multi-column index is a data structure used in relational databases that improves query performance by facilitating quick access to data. This type of index is created on two or more columns of a table, optimizing searches that involve combinations of these columns. It stores a reference to the table rows along with the indexed column values, allowing the database to quickly locate rows that meet search criteria. Multi-column indexes are particularly useful in situations where queries often filter or sort data based on multiple columns, as they can significantly reduce response time by avoiding the need to scan the entire table. However, their use must be balanced, as creating additional indexes can increase the time for inserting, updating, and deleting records due to the need to keep the index updated. Therefore, it is essential to analyze query patterns and database design to determine when and how to effectively implement multi-column indexes.
