title: How to get common records from a same table against different ids?
body: <p>I have a mysql table in my database shown below</p>
  
  <pre><code> company_id | bill_month |
   134        |Apr
   134        |May
   134        |Jun
   134        |Jul
   134        |Aug2k19
   134        |Sep2k19
   391        |Aug2k19
   391        |Sep2k19
  </code></pre>
  
  <p>Now what i want is to fetch months common to all the companies,my desired result is show below</p>
  
  <pre><code> bill_months|
   Aug2k19    |
   Sep2k19    |
  </code></pre>
  
  <p>I tried using self join with the following query</p>
  
  <pre><code> SELECT DISTINCT a.bill_month FROM bf_monthly_bill AS a INNER JOIN bf_monthly_bill AS b 
   on a.bill_month=b.bill_month WHERE a.company_id IN('134','391')
  </code></pre>