Linked from
The 11 pages that link to Database index, each with the reason it gives.
DatabaseRelated: Indexes help this database retrieve selected records without scanning every row.
Data structureRelated: Database indexes organize keys to avoid scanning every stored record.
B-treeRelated: B-trees support ordered lookups and updates in database indexes.
MySQLRelated: Indexes can make MySQL queries faster, at the cost of storage and write work.
Table (database)Related: An index can make searches on table columns faster.