查询至少具有两份工作员工的姓名和其公司名

   private void button6_Click(object sender, EventArgs e)
   {
       string s = "select employee.empname as 姓名,company.cmpname as 公司名 ";
       s += "from employee,works,company ";
       s += "where employee.empno=works.empno and company.cmpno=works.cmpno ";
       s += "and employee.empno in ";
       s += "(select empno from works group by empno having count(cmpno)>=2)";
       loadLV(listView2,s);
   }