title: how to apply filter to each row after the group by in sql
body: <p>i have a table -
  Table=emp</p>
  
  <pre><code>eno ename designation sal   mgr  deptno
  1   aaa   salesman    7000  2    10
  2   bbb   manager     17000 3    10
  3   ccc   president   40000 null 30
  4   ddd   clerk       5000  5    20
  5   eee   manager     20000 3    20
  </code></pre>
  
  <p>Q)per job how many employees earn more than 10000 ?</p>
  
  <p>i want result -</p>
  
  <pre><code>designation  count(*)
  salesman     0
  manager      2
  clerk        0
  president    1
  </code></pre>
  
  <p>query-</p>
  
  <pre><code>SELECT designation, count(*) FROM emp WHERE sal&gt;10000 GROUP BY designation;
  </code></pre>
  
  <p>getting result-</p>
  
  <pre><code>designation count(*)
  manager     2
  president   1
  </code></pre>
  
  <p>Please tell me how to apply filter on each row after group by clause ?</p>