You know the answer already: It depends. But I often see some percentage value quoted and the point of this post is to show that there is no such percentage value. To get the most out of this blog post, you should understand the basic structure for an index, i.e. how the b+ tree look like. You should also understand the difference between a clustered and a non-clustered index. In essence, you should be able to visualize these structures and searches through them as you read the text. If you find...(read more)