insert/update/delete/select query

  string ss1 = "select * from table where Scheame='" + _aaa+ "' ";

 string ss2 = "update  table  set Amount='" + _amount + "',PlcAmount='"+_amountplc+"' where id='" + _Id + "'";
             string ssss = "delete from table where CINVNO='" + _CINVNO + "'";

   string cmdsave1 = "insert into table (CINVNO,PROJECTCODE,LEDGERCODE) values('" + Mvoucherno + "','" + Mprojectcode + "','" + txtpartycode.Text + "') ";