title: mysql how to add trigger on insert to delete the first 100 rows if the rows count was 500 or 500+
body: <p>hello im new to mysql,</p>
  <p>how to make a trigger on insert to check row count if it was 500 to delete the first 100 rows.</p>
  <p>so the row count get back to 400 then add new 100 untill it reach 500 and when try to add new one the trigger delete the first 100</p>
  <p>Please don't give me other options i just want to know this answer</p>