What is the optimal length for an email address in a database?

Question

Here is an extracted portion of my query, reflecting the EMAIL_ADDRESS column data type and property:

EMAIL_ADDRESS CHARACTER VARYING(20) NOT NU         


        

Answer 1

A CHAR(20) field will always take up 20 characters, whether you use it all or not. (Often padded with spaces at the end.) A VARCHAR(20) field will take up up to 20 characters, but may take up less. One benefit of CHAR()s constant width is fast jumping to a row in a table, because you can just calculate the index it must be on. The drawback is wasting space.

The benefit of constant-sized CHAR(x)'s is lost if you have any VARCHAR(x) columns in your table. I seem to recall that MySQL silently converted any CHAR() fields into VARCHAR() behind the scenes if some columns were VARCHAR()s.