Индексы можно использовать для проверки наличия нулей и сравнения двух столбцов друг с другом.
Настройка:
create table abc
( dt date
, col_no number
, pod_cd varchar2(5)
, fant number
, rce number
, wt number )
nologging;
insert /*+ append */ into abc (dt, col_no, pod_cd, fant, rce, wt)
select case mod(rownum,3) when 0 then date '2018-12-31' + mod(rownum,1000) end
, case mod(rownum,7) when 0 then rownum end
, case mod(rownum,2) when 1 then mod(rownum,1000) end
, round(dbms_random.value) + 10
, round(dbms_random.value) + 10
, 1
from xmltable('1 to 10000000');
create index x1 on abc (pod_cd, dt);
create index x2 on abc (fant, rce);
Проверка на нулевые значения:
select count(*) from abc a
where a.pod_cd = '367'
and a.dt is null;
COUNT(*)
----------
6667
1 row selected.
Execution Plan
----------------------------------------------------------
Plan hash value: 2253536563
--------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
--------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 | 7 | 20 (0)| 00:00:01 |
| 1 | SORT AGGREGATE | | 1 | 7 | | |
|* 2 | INDEX RANGE SCAN| X1 | 6667 | 46669 | 20 (0)| 00:00:01 |
--------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
2 - access("A"."POD_CD"='367' AND "A"."DT" IS NULL)
Запрос был выполнен с использованием индекса X1, не касаясь таблицы.
Проверка на fant != rce
:
select count(*)
from abc a
where a.fant != a.rce;
COUNT(*)
----------
5000666
1 row selected.
Execution Plan
----------------------------------------------------------
Plan hash value: 29151601
------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 | 6 | 6468 (1)| 00:00:01 |
| 1 | SORT AGGREGATE | | 1 | 6 | | |
|* 2 | INDEX FAST FULL SCAN| X2 | 5000K| 28M| 6468 (1)| 00:00:01 |
------------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
2 - filter("A"."FANT"<>"A"."RCE")
Запрос был выполнен с использованием индекса X2, также не касаясь таблицы.
Проверка полного запроса:
create index x3 on abc(pod_cd, dt, fant, rce, col_no, wt);
select round(sum(a.wt)) as a_wt
from abc a
where a.dt is null
and a.col_no is not null
and a.pod_cd = '367'
and a.fant != a.rce;
A_WT
----------
481
1 row selected.
Execution Plan
----------------------------------------------------------
Plan hash value: 3828004431
--------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
--------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 | 16 | 28 (0)| 00:00:01 |
| 1 | SORT AGGREGATE | | 1 | 16 | | |
|* 2 | INDEX RANGE SCAN| X3 | 476 | 7616 | 28 (0)| 00:00:01 |
--------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
2 - access("A"."POD_CD"='367' AND "A"."DT" IS NULL)
filter("A"."COL_NO" IS NOT NULL AND "A"."FANT"<>"A"."RCE")
Полное сканирование таблицы не всегда ужасно.
SQL> drop index x1;
Index dropped.
SQL> drop index x2;
Index dropped.
SQL> drop index x3;
Index dropped.
select round(sum(a.wt)) as a_wt
from abc a
where a.dt is null
and a.col_no is not null
and a.pod_cd = '367'
and a.fant != a.rce;
A_WT
----------
481
1 row selected.
Elapsed: 00:00:00.18
Execution Plan
----------------------------------------------------------
Plan hash value: 1045519631
---------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
---------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 | 16 | 8188 (1)| 00:00:01 |
| 1 | SORT AGGREGATE | | 1 | 16 | | |
|* 2 | TABLE ACCESS FULL| ABC | 476 | 7616 | 8188 (1)| 00:00:01 |
---------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
2 - filter("A"."COL_NO" IS NOT NULL AND "A"."POD_CD"='367' AND
"A"."DT" IS NULL AND "A"."FANT"<>"A"."RCE")
Таблица AB C имеет 10 миллионов строк, и полное сканирование заняло 0,18 секунды. Это в виртуальной машине на 4-летнем ноутбуке.