[tomnipotent]

B-tree's do not work that way. They are inherently ordered, and contain min/max that help to determine if you can skip the page for a given condition. The min/max cannot be used for suffix wildcards.

Unless the index contains all the columns you're dealing with, the optimizer will determine that just scanning the table will cost less than scanning an index AND then looking up the data in the table (bookmark lookups in MSSQL).

[SigmundA]

B-trees have little to do with it, if the table has many columns its cheaper to scan the index for the value because it occupies less pages, thats all, less I/O more cache hits etc, goes from top to bottom on the index scanning for the result. This is the distinction between scan and seek.

I just ran a common one I see and yep MS SQL is still doing a index scan then key lookup to get result with a select * from table where col LIKE '%abc' type query.