Performance effect of number of columns on SELECT clause?

We did some tests using different SELECT clauses and were surprised to found how much the number of columns that were selected affect the performance.

For example, execution time of

    SELECT column1 from foobar
seems to be almost constant whatever the size of data returned in column1 is 20 - 400 bytes (only 5% decrease w/ 400 bytes).

Wheres
SELECT column1, column2, ... column13 from foobar can take even 40% longer though mo Received on Mon Feb 25 2002 - 03:32:59 CST