I am looking at my database that several people have worked on. A particular table is responding slowly when queried on a certain join. I notice some of the parameters of the join are not indexed. So I look at the indexes that are on the table and there are currently 10 of them, a lot with duplication it looks to me:
NonClustered Indexes: Index1: ManufacturerID, IsDeleted Index2: IsDeleted, ManufacturerID Index3: CustomerId Index4: IsDeleted Index5: ManufacturerId, IsDeleted, Exported Index6: ManufacturerId Index7: ManufacturerId, ModifiedOn Index8: ManufacturerId, OrderGUID Index9: SalesRepId ClusteredIndex: OrderId
The 2 columns I do join on are
So my confusion here is why do I have so may indexes that seem to contain the same columns?
Do I need an index for each of these as they look like some of them are geared towards specific queries?