3rd party app, not sure why but in their code they do varchar(36) convert of guid (no i have no idea why they would do this, just typical 3rd party apps). Unfortunately with the conversion in the where clause I end up with an index scan. i ran the same sql with the where clause using the guid value itself and went from 11K logical reads to 7. Any idea on an approach which I could try, just putting the index on the field only helps with the non conversion, it will do a seek, with conversion I get the scan.