select * vs select column

Question

If I just need 2/3 columns and I query SELECT * instead of providing those columns in select query, is there any performance degradation regarding more/less I/O

Answer 1

You should always only select the columns that you actually need. It is never less efficient to select less instead of more, and you also run into fewer unexpected side effects - like accessing your result columns on client side by index, then having those indexes become incorrect by adding a new column to the table.

[edit]: Meant accessing. Stupid brain still waking up.