(Oracle) how to group rows for pagination

ThinkJet is right that that some of the other answers don't cater for the 'keep together' requirement. However I think this can be done without resorting to a user-defined aggregate.

Sample data

create table test (empno number, ename varchar2(20), trandate date, amt number);insert into test values (100, 'Alison'   ,  to_date('21-MAR-1996') ,   45000);insert into test values (100, 'Alison'   ,  to_date('12-DEC-1978') ,   23000);insert into test values (100, 'Alison'   ,  to_date('24-OCT-1982') ,   11000);insert into test values (101, 'Linda'    ,  to_date('15-JAN-1984') ,   16000);insert into test values (101, 'Linda'    ,  to_date('30-JUL-1987') ,   17000);insert into test values (102, 'Celia'    ,  to_date('31-DEC-1990') ,   78000);insert into test values (102, 'Celia'    ,  to_date('17-SEP-1996') ,   21000);insert into test values (103, 'James'    ,  to_date('21-MAR-1996') ,   45000);insert into test values (103, 'James'    ,  to_date('12-DEC-1978') ,   23000);insert into test values (103, 'James'    ,  to_date('24-OCT-1982') ,   11000);insert into test values (104, 'Robert'   ,  to_date('15-JAN-1984') ,   16000);insert into test values (104, 'Robert'   ,  to_date('30-JUL-1987') ,   17000);

Now, determine the end row of each empno segment (using RANK to find the start and COUNT..PARTITION BY to find the number in the segment).

Then use ceil/4 from APC's solution to group them into their 'pages'. Again, as pointed out by ThinkJet, there is a problem in the specification as it doesn't cater for the situation when there are more records in the empno 'keep together' segment than can fit in a page.

select empno, ename,       ceil((rank() over (order by empno) +         count(1) over (partition by empno))/6) as chunkfrom testorder by 1;

As pointed out by ThinkJet, this solution isn't bullet proof.

drop table test purge;create table test (empno number, ename varchar2(20), trandate date, amt number);declare    cursor csr_name is    select rownum emp_id,              decode(rownum,1,'Alan',2,'Brian',3,'Clare',4,'David',5,'Edgar',             6,'Fred',7,'Greg',8,'Harry',9,'Imran',10,'John',             11,'Kevin',12,'Lewis',13,'Morris',14,'Nigel',15,'Oliver',             16,'Peter',17,'Quentin',18,'Richard',19,'Simon',20,'Terry',             21,'Uther',22,'Victor',23,'Wally',24,'Xander',             25,'Yasmin',26,'Zac') emp_name    from dual connect by level <= 26;begin  for c_name in csr_name loop    for i in 1..11 loop       insert into test values            (c_name.emp_id, c_name.emp_name, (date '2010-01-01') + i,             to_char(sysdate,'SS') * 1000);    end loop;  end loop;end;/select chunk, count(*)from  (select empno, ename,       ceil((rank() over (order by empno) +         count(1) over (partition by empno))/25) as chunk  from test)group by chunkorder by chunk;

So with chunk size of 25 and group size of 11, we get the jumps where it fits 33 people in the chunk despite the 25 limit. Large chunk sizes and small groups should make this infrequent, but you'd want to allow some leeway. So maybe set the chunks to 65,000 rather than going all the way to 65,536.

It's too tricky or even impossible to do such thing in plain SQL.

But with some limitations problem can be resolved with help of user-defined aggregate functions .

First, create object with ODCIAggregate interface implementation:

create or replace type page_num_agg_type as object(  -- Purpose : Pagination with "leave together" option  -- Attributes               -- Current page number  cur_page_number    number,                                   -- Cumulative number of rows per page incremented by blocks  cur_page_row_count number,  -- Row-by-row counter for detect page overflow while placing single block  page_row_counter   number,  -- Member functions and procedures  static function ODCIAggregateInitialize(    sctx in out page_num_agg_type  )  return number,  member function ODCIAggregateIterate(    self        in out page_num_agg_type,    value       in     number  )  return number,  member function ODCIAggregateTerminate(    self        in   page_num_agg_type,    returnValue out  number,    flags       in   number  )  return number,  member function ODCIAggregateMerge(    self in out page_num_agg_type,    ctx2 in     page_num_agg_type  )  return number);

Create type body:

create or replace type body PAGE_NUM_AGG_TYPE is  -- Member procedures and functions  static function ODCIAggregateInitialize(    sctx in out page_num_agg_type  )    return number  is  begin      sctx := page_num_agg_type(1, 0, 0);      return ODCIConst.Success;  end;  member function ODCIAggregateIterate(    self        in out page_num_agg_type,    value       in     number )   return number is   -- !!! WARNING: HARDCODED !!!   RowsPerPage number := 4; begin   self.page_row_counter := self.page_row_counter + 1;   -- Main operations: determine number of page   if(value > 0) then      -- First row of new block    if(self.cur_page_row_count + value > RowsPerPage) then       -- If we reach next page with new block of records - switch to next page.       self.cur_page_number := self.cur_page_number + 1;       self.cur_page_row_count := value;       self.page_row_counter := 1;    else       -- Just increment rows and continue to place on current page       self.cur_page_row_count := self.cur_page_row_count + value;    end if;   else                            -- Row from previous block     if(self.page_row_counter > RowsPerPage) then        -- Single block of rows exceeds page size - wrap to next page.       self.cur_page_number := self.cur_page_number + 1;       self.cur_page_row_count := self.cur_page_row_count - RowsPerPage;       self.page_row_counter := 1;     end if;   end if;   return ODCIConst.Success; end; member function ODCIAggregateTerminate(   self        in page_num_agg_type,   returnValue out number,   flags       in number )   return number is begin   -- Returns current page number as result   returnValue := self.cur_page_number;   return ODCIConst.Success; end; member function ODCIAggregateMerge(   self in out page_num_agg_type,   ctx2 in     page_num_agg_type )   return number is begin   -- Can't act in parallel - error on merging attempts   raise_application_error(-20202,'PAGE_NUM_AGG_TYPE can''t act in parallel mode');   return ODCIConst.Success; end;end;

Create agrreation function to use with type:

create function page_num_agg (  input number) return number aggregate using page_num_agg_type;

Next prepare data and use new function to calculate page numbers:

with data_list as (  -- Your example data as source  select 100 as EmpNo, 'Alison' as EmpName, to_date('21-MAR-96','dd-mon-yy') as TranDate, 45000 as AMT from dual union all  select 100 as EmpNo, 'Alison' as EmpName, to_date('12-DEC-78','dd-mon-yy') as TranDate, 23000 as AMT from dual union all  select 100 as EmpNo, 'Alison' as EmpName, to_date('24-OCT-82','dd-mon-yy') as TranDate, 11000 as AMT from dual union all  select 101 as EmpNo, 'Linda'  as EmpName, to_date('15-JAN-84','dd-mon-yy') as TranDate, 16000 as AMT from dual union all  select 101 as EmpNo, 'Linda'  as EmpName, to_date('30-JUL-87','dd-mon-yy') as TranDate, 17000 as AMT from dual union all  select 102 as EmpNo, 'Celia'  as EmpName, to_date('31-DEC-90','dd-mon-yy') as TranDate, 78000 as AMT from dual union all  select 102 as EmpNo, 'Celia'  as EmpName, to_date('17-SEP-96','dd-mon-yy') as TranDate, 21000 as AMT from dual union all  select 103 as EmpNo, 'James'  as EmpName, to_date('21-MAR-96','dd-mon-yy') as TranDate, 45000 as AMT from dual union all  select 103 as EmpNo, 'James'  as EmpName, to_date('12-DEC-78','dd-mon-yy') as TranDate, 23000 as AMT from dual union all  select 103 as EmpNo, 'James'  as EmpName, to_date('24-OCT-82','dd-mon-yy') as TranDate, 11000 as AMT from dual union all  select 104 as EmpNo, 'Robert' as EmpName, to_date('15-JAN-84','dd-mon-yy') as TranDate, 16000 as AMT from dual union all  select 104 as EmpNo, 'Robert' as EmpName, to_date('30-JUL-87','dd-mon-yy') as TranDate, 17000 as AMT from dual union all  select 105 as EmpNo, 'Monica' as EmpName, to_date('30-JUL-88','dd-mon-yy') as TranDate, 31000 as AMT from dual union all  select 105 as EmpNo, 'Monica' as EmpName, to_date('01-JUL-87','dd-mon-yy') as TranDate, 19000 as AMT from dual union all  select 105 as EmpNo, 'Monica' as EmpName, to_date('31-JAN-97','dd-mon-yy') as TranDate, 11000 as AMT from dual union all  select 105 as EmpNo, 'Monica' as EmpName, to_date('17-DEC-93','dd-mon-yy') as TranDate, 33000 as AMT from dual union all  select 105 as EmpNo, 'Monica' as EmpName, to_date('11-DEC-91','dd-mon-yy') as TranDate, 65000 as AMT from dual union all  select 105 as EmpNo, 'Monica' as EmpName, to_date('22-OCT-89','dd-mon-yy') as TranDate, 19000 as AMT from dual ),ordered_data as (  select                -- Source table fields    src_data.EmpNo, src_data.EmpName, src_data.TranDate, src_data.AMT,    -- Calculate row count per one employee    count(src_data.EmpNo) over(partition by src_data.EmpNo)as emp_row_count,    -- Calculate rank of row inside employee data sorted in output order    rank() over(partition by src_data.EmpNo order by src_data.EmpName, src_data.TranDate) as emp_rnk  from     data_list src_data)  -- Final step: calculate page number for rowsselect     -- Source table data    ordered_data.EmpNo, ordered_data.EmpName, ordered_data.TranDate, ordered_data.AMT,     -- Aggregate all data with our new function    page_num_agg(      -- pass count of rows to aggregate function only for first employee's row      decode(ordered_data.emp_rnk, 1, ordered_data.emp_row_count, 0)     )       over (order by ordered_data.EmpName, ordered_data.TranDate) as page_numberfrom      ordered_data    order by   ordered_data.EmpName, ordered_data.TranDate

And, finally ...

Disadvantages of this solution:

1. Hardcoded page row count.
2. Requires some specific data preparation in query to use aggregate function properly.

Advantages of this solution:

1. Just works :)

Updated: improved to handle oversized blocks, example modified.

The following SQL statement splits the twenty records in my EMP table into five pages of four rows each:

SQL> select empno  2         , ename  3         , deptno  4         , ceil((row_number() over (order by deptno, empno)/4)) as pageno  5  from emp  6  /     EMPNO ENAME          DEPTNO     PAGENO---------- ---------- ---------- ----------      7782 BOEHMER            10          1      7839 SCHNEIDER          10          1      7934 KISHORE            10          1      7369 CLARKE             20          1      7566 ROBERTSON          20          2      7788 RIGBY              20          2      7876 KULASH             20          2      7902 GASPAROTTO         20          2      7499 VAN WIJK           30          3      7521 PADFIELD           30          3      7654 BILLINGTON         30          3      7698 SPENCER            30          3      7844 CAVE               30          4      7900 HALL               30          4      8083 KESTELYN           30          4      8084 LIRA               30          4      8060 VERREYNNE          50          5      8061 FEUERSTEIN         50          5      8085 TRICHLER           50          5      8100 PODER              50          520 rows selected.SQL>