title: how to prevent of duplicating records in mysql insertion queries?
body: <p>i always in inserting data into a mysql table i use a select for that data before inserting to avoid duplicate records and if the query return null then i insert record.</p>
  
  <p>but i think maybe it is not a professional way to do this job.</p>
  
  <p>would you let me the ways you do?</p>