All Indexes in the SQL Server database will be fragmented After related tables got many update, delete transactions.
If the index in the table is fragmented then all transactions related with that table will be very slow. So SQL Server DBA should frequently monitor indexes and which of indexes are fragmented and which are not like following screenshot.
You can check fragmented index with following script. Type SQL Server Database name is correctly in the first line then query will find fragmented indexes.
declare @db int select @db=DB_ID('DEVECI')
select 'ALTER INDEX [' + i.name +'] on '+OBJECT_NAME(s.object_id)+' REBUILD WITH (ONLINE = ON)', objname = OBJECT_NAME(s.object_id), s.object_id, index_name= i.name, index_type_desc, avg_fragmentation_in_percent from sys.dm_db_index_physical_stats(@db,null,null,null,null) as s join sys.indexes i on i.object_id = s.object_id and i.index_id = s.index_id where avg_fragmentation_in_percent>30 order by avg_fragmentation_in_percent desc, page_count desc;