SQL statement with LIMIT and total count?

Question

Hello,
I would like to know if it is possible to execute a single SQL statement that will return me a subset of data (for pagination purposes) that not only includes the subset of data for the page but the count of all available data. Can this be done so as to not take up the cpu and time it takes to essentially run two queries? One to get the subset and one to get the count? I think simply doing a subselect is not going to give me what I want in that we actually query twice.
There may be no way to do this other than that, but I wanted to check with the gurus here first. :)
Thanks,
Mark

Answer 1

select *
from (
select i.*,
row_number() over(order by i) rn, -- used for
pagination
count(*) over(partition by 1) cnt  -- total count
of rows found for this search
from mytable
where < PUT ALL LIMITING (i.e., "search") CONDITIONS
HERE >
where rn between 41 and 50 -- pagination clauseNice one
BUT of course it adds additional row in execution plan and takes additional time and CPU :)
I assume that it directly depends of course on returned result set and some other factors like available sort space but a simple test case on a table big which actually is 1.6 M rows like dba_source got following results:
here is the first one returning also count(*)
SQL> select *
  2  from (
  3    select i.*,
  4      row_number() over(order by owner, name, type) rn
  5  , -- used for pagination
  6      count(*) over(partition by 1) cnt  -- total count of rows found for this search
  7    from big i
  8    where owner like 'S%' and name like '%A%'
  9  )
10  where rn between 41 and 45
11  /
OWNER                          NAME                           TYPE
      LINE
TEXT
        RN        CNT
SYS                            ANYDATA                        TYPE
        13
  STATIC FUNCTION ConvertVarchar(c IN VARCHAR) return AnyData,
        41     999744
SYS                            ANYDATA                        TYPE
        11
  STATIC FUNCTION ConvertDate(dat IN DATE) return AnyData,
        42     999744
SYS                            ANYDATA                        TYPE
         9
        43     999744
SYS                            ANYDATA                        TYPE
         7
     They serve as explicit CAST functions from any type in the Oracle ORDBMS
        44     999744
SYS                            ANYDATA                        TYPE
         6
     enable construction of the AnyData in its entirity with a single call.
        45     999744
Elapsed: 00:00:41.02
SQL> ed
Wrote file afiedt.buf
  1  select n.name, m.value from v$statname n, v$mystat m
  2  where n.statistic# = m.statistic#
  3*   and (upper(name) like '%SORT%' or upper(name) like '%TEMP%')
SQL> /
NAME                                                                  VALUE
physical reads direct temporary tablespace                            35446
physical writes direct temporary tablespace                           17723
RowCR attempts                                                            0
SMON posted for dropping temp segment                                     0
sorts (memory)                                                           36
sorts (disk)                                                              1
sorts (rows)                                                        1999596
OTC commit optimization attempts                                          0
8 rows selected.here is the second one returning only rows:
SQL> ed
Wrote file afiedt.buf
  1  select *
  2  from (
  3    select i.*,
  4      row_number() over(order by owner, name, type) rn
  5  --, -- used for pagination
  6  --    count(*) over(partition by 1) cnt  -- total count of rows found for this search
  7    from big i
  8    where owner like 'S%' and name like '%A%'
  9  )
10* where rn between 41 and 45
SQL> /
OWNER                          NAME                           TYPE
      LINE
TEXT
        RN
SYS                            ANYDATA                        TYPE
        13
  STATIC FUNCTION ConvertVarchar(c IN VARCHAR) return AnyData,
        41
SYS                            ANYDATA                        TYPE
        11
  STATIC FUNCTION ConvertDate(dat IN DATE) return AnyData,
        42
SYS                            ANYDATA                        TYPE
         9
        43
SYS                            ANYDATA                        TYPE
         7
     They serve as explicit CAST functions from any type in the Oracle ORDBMS
        44
SYS                            ANYDATA                        TYPE
         6
     enable construction of the AnyData in its entirity with a single call.
        45
Elapsed: 00:00:12.09
SQL> select n.name, m.value from v$statname n, v$mystat m
  2  where n.statistic# = m.statistic#
  3    and (upper(name) like '%SORT%' or upper(name) like '%TEMP%')
  4  /
NAME                                                                  VALUE
physical reads direct temporary tablespace                                0
physical writes direct temporary tablespace                               0
RowCR attempts                                                            0
SMON posted for dropping temp segment                                     0
sorts (memory)                                                           10
sorts (disk)                                                              0
sorts (rows)                                                         999812
OTC commit optimization attempts                                          0
8 rows selected.So execution time 41 sec vs 12 sec
sorts (rows) 1 999 596 vs 999 812
physical reads/writes direct temporary tablespace 35446/17723 vs 0/0
I assume that for a small overall returned row count it probably is OK, but for less restrictive search it can be quite deadly as before with two queries.
Gints Plivna
http://www.gplivna.eu