Does inserting/updating/deleting record auto update indexes?

Question

Does inserting/ updating or deleting a record in DB auto update the indexes?

I've seen rebuild commands for indexes and I just can't understand if I have to do all these manually, then what's the purpose of indexes. This is so inconvenient that I spend time rebuilding the indexes every week or so.

Answer 1

When index fragmentation becomes too high, indexes will be very inefficient. There is need to rebuild index.

Let SQL Server Tell You Which Indexes to Rebuild

Rebuilding an index drops and re-creates the index. This removes fragmentation, reclaims disk space by compacting the pages based on the existing fill factor setting, and reorders the index rows in contiguous pages.

Reorganizing and Rebuilding Indexes

Answer 2

Yes, when you insert, update, or delete a row, any indexes on that table automatically reflect the change.