Preordering the table by a specified column

I have a table and I am always getting the data by ordering a column. In my case, I order by datenum. However, the selection is so slow because of the ordering.

Is it possible to order the table after datenum. This column is defined as unique. If defined as an index, would the selection will be faster?

• There is no natural, implied or intrinsic ordering to a table

• Any order is only guaranteed by the outermost ORDER BY

If this is slow, then you can either

• make the index covering (a UNIQUE constraint is an index already)

• make it the clustered index (which is covering by its nature)

StackExchange Database Administrators Q#5160, answer score: 5