title: Are there any disadvantages to using column charset different to schema default in MySQL?
body: <p>In my application, I am storing ids in a table as char(16), calculated as hex(uuid_short()) to make it usable with memcached plugin which requires 'key' to be a char or varchar.
  <strong>Example value: 57F328CF000003</strong></p>
  
  <p>If I leave it to default characterset which is utf8, as per <a href="http://dev.mysql.com/doc/refman/5.7/en/charset-unicode-utf8.html" rel="nofollow">docs</a> it will use 3x16 bytes becaues utf8 can have max 3 bytes.
  However for the possible values in my use case (which is 1-9 digits and A-F), 1 byte ascii character set is sufficient. </p>
  
  <p>I am unsure about whether it is a good idea to change just the column or just the table to use ascii char set? Are there any performance or design implications to using a different charset to the default of schema or the table? Are there any implications to the collation at all? <em>Currently I use default char set 'utf8' and default collation 'utf8_general_ci'.</em></p>