Why is doing a top(1) on an indexed column in SQL Server slow?

Question

I\'m puzzled by the following. I have a DB with around 10 million rows, and (among other indices) on 1 column (campaignid_int) is an index.

Now I have 700k rows wher

Answer 1

Due to the statistics, you should explicitly ask the optimizer to use the index you've created instead of the clustered one.

SELECT  TOP (1) connectionid
FROM    outgoing_messages WITH (NOLOCK, index(idx_connectionid))
WHERE  (campaignid_int = 3835)

I hope it will solve the issue.

Regards, Enrique