Being new in SAS SQL Indexes, I got confused with understanding of  the following options:     When IDXWHERE = option is: Yes-SAS uses the best available index to process the WHERE               Expression, even if SAS estimates that sequential access is               Faster NO- SAS process the data sequentially even if SAS estimates that             Processing with an index is better     I just wonder ….what might be hypothetical cases when both cases are applicable? Could you please give me any example why it might be in need?   Thank you in advance,   Irin