I have inherited a database that I am wondering about optimizing the column sizes. There are many varchar columns that are overly generous in their sizes. For example, varchar(100) where the data is routinely 20 characters or less and probably never over 30 characters wide.
Similarly, there are other fields that are way too generous for the forseeable data.
My question is: how much of a performance penalty are we paying for column sizes that are overly generous?