统计sql有关问题

select bb,       sum(decode(to_char(aa,'yyyy-mm'),'2012-01',1,0)) c1,       --...       sum(decode(to_char(aa,'yyyy-mm'),'2012-04',1,0)) c4,       sum(decode(to_char(aa,'yyyy-mm'),'2012-05',1,0)) c5       --...from t1group by bb
------解决方案--------------------
申明2维数组，以下是一个实例，仅供参考。可能有不好的地方。
  


SQL code
  --按日统计受理后学员报表数据  function fun_student_total_rep(schoolId in varchar2,startDate in date,endDate in date,rep_type in number)   return clob   is   days int :=endDate-startDate+1;   i int :=1;   j int :=1;   var_temp_index int;   var_count int:=0;   var_temp_school_name varchar2(20);   var_temp_str varchar2(20);   var_temp_length int:=0;   var_return clob;   type typeDateArray is table of varchar2(20) index by binary_integer;   type dateArray is table of binary_integer index by varchar2(10);   type twoArray is table of typeDateArray index by binary_integer;   var_dataDate typeDateArray;   var_temp_dataDate typeDateArray;   var_twoArray twoArray;   --日期对应列表下标   var_date dateArray;   type typeCur is ref cursor;   cur_data typeCur;   var_sql varchar2(400);   vc_id t_student_total_report.id%type;   vc_nums number;   vc_school_name varchar(40);   vc_date date;   begin     var_dataDate(0):='驾校名称';     var_dataDate(days+1):='小计';     --生成标题     for tempI in 1.. days loop     --生成标题02-28日(人),只保留月与日       var_dataDate(tempI):=substr(to_char(startDate+tempI-1,'yyyy-mm-dd'),6,9)||'日(人)';       var_date(to_char(startDate+tempI-1,'yyyy-mm-dd')):=tempI;       var_twoArray(0):=var_dataDate;     end loop;     --重置默认值0     for tempI in 1.. days loop       var_dataDate(tempI):='0';     end loop;    var_sql:='select t.id,         t.total_num as nums,         t.school_name,         trunc(t.report_date) as report_date    from t_student_total_report t, corp_info c   where report_date >=to_date('''||to_char(startDate,'yyyy-mm-dd')||''',''yyyy-mm-dd'''||      ') and report_date <=to_date('''||to_char(endDate,'yyyy-mm-dd')||''',''yyyy-mm-dd'''||      ') and t.school_id = c.school_id';   if schoolId is not null then      var_sql:=var_sql||' and t.school_id= '''||schoolId||'''';      dbms_output.put_line(var_sql);   end if;   var_sql:=var_sql||' order by c.sort_id, t.report_date';     --生成数据     open cur_data for var_sql;     loop          fetch cur_data into vc_id,vc_nums,vc_school_name,vc_date;          exit when cur_data%Notfound;          if var_temp_school_name is not null and var_temp_school_name !=vc_school_name  then          --一条记录          j:=j+1;          var_count :=0;          --重置默认值0         for tempI in 1.. days loop           var_dataDate(tempI):='0';         end loop;       end if;       --0，驾校名称       var_temp_index:= var_date(to_char(vc_date,'yyyy-mm-dd'));       var_temp_school_name:=vc_school_name;       var_dataDate(var_temp_index):=vc_nums;       var_dataDate(0):=var_temp_school_name;       --驾校小计统计       var_count :=var_count+vc_nums;       --小计       var_dataDate(days+1):=var_count;       --每个驾校的记录       var_twoArray(j):=var_dataDate;     end loop;     if j =1 and var_temp_school_name is null then       var_dataDate(0):='';       var_dataDate(days):='0';       var_dataDate(days+1):='0';       var_twoArray(j):=var_dataDate;     else       var_dataDate(0):=var_temp_school_name;       var_dataDate(days+1):=var_count;       var_twoArray(j):=var_dataDate;     end if;     --驾校的受理人员数量   --  dbms_output.put_line('var_twoArray.count = '||var_twoArray.count);     --计算日合计     for x in 1..var_twoArray.count loop       if not var_twoArray.exists(x) then         exit;       end if;       var_dataDate :=var_twoArray(x);      -- dbms_output.put_line('x = '||x);       for m in 1.. var_dataDate.count loop         if not var_dataDate.exists(m) then           exit;         end if;        -- dbms_output.put('m = '||m);         dbms_output.put('value = '||var_dataDate(m));         if not var_temp_dataDate.exists(m) then           var_temp_dataDate(m):=var_dataDate(m);         else           var_temp_dataDate(m):=var_temp_dataDate(m)+var_dataDate(m);         end if;       end loop;       dbms_output.put_line(' ');     end loop;     var_temp_dataDate(0):='合计';     var_twoArray(var_twoArray.count):=var_temp_dataDate;     --打印,拼装     for x in 0..var_twoArray.count loop       if not var_twoArray.exists(x) then         exit;       end if;       var_dataDate :=var_twoArray(x);      -- dbms_output.put_line('x = '||x);       for m in 0.. var_dataDate.count loop         if not var_dataDate.exists(m) then           exit;         end if;        -- dbms_output.put('m = '||m);      --   dbms_output.put('value = '||var_dataDate(m));         var_temp_str:='^^';         var_return :=var_return||var_dataDate(m)||'^^';       end loop;   --    dbms_output.put_line('var_return'||var_return);       var_return :=var_return||'$$';     end loop;     return var_return;   end fun_student_total_rep;