Nonclustered index with include vs nearly same Nonclustered index without; Multiple query coverage
I have two existing indices in a DB as below
CREATE NONCLUSTERED INDEX IndexTable1 ON Table (fkAnothertable)
CREATE NONCLUSTERED INDEX IndexTable2 ON Table (fkAnothertable) INCLUDE (pkTable)
I had a hunch and my research seems to point that any queries that call #1 would be satisfied by #2 and that #1 is wasteful. I couldn't find a definitive answer though.
Is this assumption correct and can I drop #1 and potentially improve performance?
Yes. #2 entirely covers #1 and possibly vice-versa in fact. Is pkTable your clustered index key? If so that will be included in #1 (at the key level because the non clustered index is not declared as unique).
If pkTable is not the clustering key then queries seeking on #1 will still be satisfied by #2 but #2 may occupy more pages thus making scans that would have used #1 a tad less efficient.