Recently, I have observed that not many people have proper understanding of what is bookmark lookup or key lookup. Increasing numbers of the questions tells me that this is something that developers encounter every single day, but have no idea how to deal with. I have previously written three posts on this subject. All those who are looking for further information can check out the following three posts.
SQL SERVER – Interesting Observation – Execution Plan and Results of Aggregate Concatenation Queries
In one of my recent classes, we had an in-depth conversation on what are the alternatives of creating covering indexes to remove the bookmark lookup. I really want to keep this question open to all of you and see what community thinks about the same. Is there any way other than creating a covering index or included index to remove this expensive keylookup?
Reference: Pinal Dave (https://blog.sqlauthority.com)
