An index is a data structure that improves search speed.
It allows the database to locate rows quickly.
Indexes reduce full table scans.
Without indexes, SQL must scan every row.
This becomes slow for large tables.
Indexes help skip unnecessary rows.
Indexes store column values in sorted order.
They maintain references to table rows.
This enables faster lookup.
When a query uses an indexed column, the optimizer chooses index scan.
This significantly improves performance.
Indexes increase read speed but slow write operations.
They must be used carefully.
Balanced indexing is key to performance tuning.