(Oracle) how to group rows for pagination - sql

Question

I have a table that outputs similar to this (although in thousands):
EMPNO ENAME TRANDATE AMT
---------- ---------- --------- -------
100 Alison 21-MAR-96 45000
100 Alison 12-DEC-78 23000
100 Alison 24-OCT-82 11000
101 Linda 15-JAN-84 16000
101 Linda 30-JUL-87 17000
102 Celia 31-DEC-90 78000
102 Celia 17-SEP-96 21000
103 James 21-MAR-96 45000
103 James 12-DEC-78 23000
103 James 24-OCT-82 11000
104 Robert 15-JAN-84 16000
104 Robert 30-JUL-87 17000
My desired output would be similar to this:
EMPNO ENAME TRANDATE AMT PAGE
---------- ---------- --------- ------- ----
100 Alison 21-MAR-96 45000 1
100 Alison 12-DEC-78 23000 1
100 Alison 24-OCT-82 11000 1
101 Linda 15-JAN-84 16000 2
101 Linda 30-JUL-87 17000 2
102 Celia 31-DEC-90 78000 2
102 Celia 17-SEP-96 21000 2
103 James 21-MAR-96 45000 3
104 Robert 12-DEC-78 23000 4
104 Robert 24-OCT-82 11000 4
104 Robert 15-JAN-84 16000 4
104 Robert 30-JUL-87 17000 4
Basically, it should insert a new field to identify the page it belongs to. The page break is based on the rows. And, as if "kept together" in EMPNO, it adds 1 to PAGE when the rows cannot add the next EMPNO batch. It's for the Excel limit since Excel does not allow more than 65000 rows (or so) in a single Sheet. In the sample's case, it's only 4 rows. The limit number is static.

Answer 1

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 chunk
from test
order 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 chunk
order 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.

Answer 2

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 rows
select
-- 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_number
from
ordered_data
order by
ordered_data.EmpName, ordered_data.TranDate
And, finally ...
Disadvantages of this solution:
Hardcoded page row count.
Requires some specific data preparation in query to use aggregate function properly.
Advantages of this solution:
Just works :)
Updated: improved to handle oversized blocks, example modified.

Answer 3

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 5
20 rows selected.
SQL>

Answer 4

How about this one: (100 is the row limit per page)
select
a.*, floor(count(1) over (order by empno, empname)/100)+1 as page
from source_table a
order by page, empno, empname;