title: MySQL-Update table takes so long
body: <p>I have a talbe with ~110k rows and 20 columns and no indexes. I wrote a query to update 9 columns of this table JOIN with another table which has many indexes. And the query took forever to run. I really dont know why. Here is my query:</p>
  
  <pre><code>UPDATE tonghop a JOIN testdone b 
  ON a.stt = b.stt 
  SET a.source = b.source, a.pid=b.pid, a.tenbenhnhan = b.fullname, 
  a.orderdoctor=b.orderdoctor, a.specialty = b.specialty, a.rdate = b.rdate, 
  a.icd_code = b.icd_code, a.servicegroup = b.servicegroup;
  </code></pre>
  
  <p>Really appreciate if someone could help </p>