column indexing and sql profiler

Question

I have enabled sql profiler and identified several queries that are taking a long time to execute.

For example:

Select A from table_A where B = 2

My question is, based on above query, do I create indexes on column A or B? or A and B?

Answer 1

Index on B including column A. The where can use a seek on B while still returning A.

Answer 2

Your index should be on B since that's what is in your condition. You might benefit from just trying out all the ways and looking at the resulting execution plans.

Answer 3

I would create an index on column B because that is what sql server is doing the comparison on. Afterwards I would run the profiler again to see if adding the index negatively impacts other queries.

Answer 4

Create seperate indexes on B and A. Creating index on A is to avoid KEY LOOKUP.