Does mySQL update statement actually update all fields in the background?
<p>This might be a simple question that somebody already might have an answer.  When an UPDATE statement for MySQL is sent to the MySQL server even with only specific fields to be updated, does the server actually update all the fields in the row?  We have some issues trying to understand the server transaction log. </p>

<p>Basically I want to understand the inner workings of the MySQL server.  Does it create the record set with all the values and the override the old record set with the new one or does it only pick the specific fields in the records and only update that.</p>

<p>TL;DR:  If each record set is a binary memory section, does the entire memory section get updated even if specific fields of the record is chosen for update?</p>