I am tuning a database created by someone else.
I noticed that some column lengths were defined longer than needed.
For example, an Id column is holding a stand length of 20 characters but was defined as varchar(255).
On some other columns, for example, a Description column is supposed to hold less than 100 characters but defined as text.
I am trying to understand the performance impact if a column is over defined in the following cases:
1. char(20) vs varchar(20)
2. varchar(20) vs varchar(255)
3. varchar(255) vs text
thanks,
Jessica