Oracle语句优化之一

public List<TdDepartment> createZtreeDep(String compId) {

        List<TdDepartment> dd = new ArrayList<TdDepartment>();
       //查找所有子部门的sql语句　　　　 String sql = "select dep_id,dep_name,super_id,folder from td_department "+
                        "start with super_id in ( "+
                        "select dep_id  from td_department "+
                        "where valid_flag = ‘Y‘  and comp_id = ‘"+compId+"‘)connect by prior dep_id = super_id";        　　　　//查找部门本身的sql语句
        String parentsql = "select dep_id ,dep_name,super_id,folder  from td_department "+
                    "where valid_flag = ‘Y‘  and comp_id = ‘"+compId+"‘";
        EpDB db = new EpDB();
        ArrayList<HashMap> parentdeparts = db.getHashData(parentsql);
        ArrayList<HashMap> departs = db.getHashData(sql);
        if(parentdeparts == null || parentdeparts.size() <= 0)
            return null;      　　　　//将部门加入到list中
        for(int i=0; i<parentdeparts.size(); i++){
            String dep_id = parentdeparts.get(i).get("DEP_ID").toString();
            String dep_name = parentdeparts.get(i).get("DEP_NAME").toString();
            String super_id = parentdeparts.get(i).get("SUPER_ID").toString();
            TdDepartment td = new TdDepartment();
            td.setId(dep_id);
            td.setPid(super_id);
            td.setName(dep_name);
            if(parentdeparts.get(i).get("FOLDER") != null){
                String folder = parentdeparts.get(i).get("FOLDER").toString();
                if("Y".equals(folder)){
                    td.setOpen("true");//非叶子结点则需要展开
                }else{
                    td.setOpen("false");
                }
            }
            //取消循环读取
            //td.setChild(createDepartments(dep_id));
            dd.add(td);
        }
　　　　　//将子部门加入到list中　
        for(int i=0; i<departs.size(); i++){
            String dep_id = departs.get(i).get("DEP_ID").toString();
            String dep_name = departs.get(i).get("DEP_NAME").toString();
            String super_id = departs.get(i).get("SUPER_ID").toString();
            TdDepartment td = new TdDepartment();
            td.setId(dep_id);
            td.setPid(super_id);
            td.setName(dep_name);
            if(departs.get(i).get("FOLDER") != null){
                String folder = departs.get(i).get("FOLDER").toString();
                if("Y".equals(folder)){
                    td.setOpen("true");//非叶子结点则需要展开
                }else{
                    td.setOpen("false");
                }
            }
            //取消循环读取
            //td.setChild(createDepartments(dep_id));
            dd.add(td);
        }

        return dd;
    }

需要优化点：

思考一：通过sql语句的优化来优化

思考二：通过程序递归的方法来优化