java - How to sum data from specific record? -

    ___worker_id___|_______occur________           20       |         1           20       |         2           21       |         3           22       |         5           20       |         1       according table, need know each worker how many occur?      such   worker_id=20 has occur 4                   worker_id=21 has occur 8 

i can 2 value worker table code

         string sql = "select table.worker_id,table.occur keyword_pages table"             + " keyword_id=" + puid;          conn = getconnection();         stm = conn.createstatement();         rs = stm.executequery(sql);         while (rs.next()) {             int kwd_id = rs.getint(1);    /**worker_id 20,20,21,22,20*/             int occur = rs.getint(2);     /**worker_id 1,2,3,5,1*/                    } 

how amount of occur each worker?

this coding. use hashmap store each record. , store hashmap linklist. haven't idea result.

  conn = getconnection();         stm = conn.createstatement();         rs = stm.executequery(sql);         while (rs.next()) {             int kwd_id = rs.getint(1);             int occur = rs.getint(2);             hmap.put(kwd_id, occur);             listid.add(hmap);             //system.out.println(kwd_id +"  |  "+ occur);         }          (int = 0; < listid.size(); i++) {           }           

string sql = "select t.worker_id, sum(t.occur) osum"         + " keyword_pages t"         + " keyword_id=" + puid         + " group t.worker_id"; 

now rs.getint(2) or rs.getint("osum") give group's sum.