ORACLE:Материализираният изглед не работи при използване на LEFT JOIN

Има две условия, които не са изпълнени, за да може този материализиран изглед да се опреснява бързо. Първият е, че не сте посочили колоните rowid на всяка включена таблица. И второто е недокументирано ограничение:ANSI-съединенията не се поддържат.

Ето пример с DEPT е table_1, псевдоним a и EMP е table_2, псевдоним b:

SQL> create materialized view log on emp with rowid
  2  /

Materialized view log created.

SQL> create materialized view log on dept with rowid
  2  /

Materialized view log created.

SQL> create materialized view empdept_mv
  2    refresh fast on commit
  3  as
  4  select a.deptno
  5    from dept a
  6         left join emp b on (a.deptno = b.deptno)
  7  /
  from dept a
       *
ERROR at line 5:
ORA-12054: cannot set the ON COMMIT refresh attribute for the materialized view

Това имитира вашата ситуация. Първо добавете rowid's:

SQL> create materialized view empdept_mv
  2    refresh fast on commit
  3  as
  4  select a.rowid dept_rowid
  5       , b.rowid emp_rowid
  6       , a.deptno
  7    from dept a
  8         left join emp b on (a.deptno = b.deptno)
  9  /
  from dept a
       *
ERROR at line 7:
ORA-12054: cannot set the ON COMMIT refresh attribute for the materialized view

Все пак не може да се опресни бързо, поради ANSI присъединяванията. Преобразуване към синтаксис на външно съединение в стар стил:

SQL> create materialized view empdept_mv
  2    refresh fast on commit
  3  as
  4  select a.rowid dept_rowid
  5       , b.rowid emp_rowid
  6       , a.deptno
  7    from dept a
  8       , emp b
  9   where a.deptno = b.deptno (+)
 10  /

Materialized view created.

И за да докажете, че работи:

SQL> select * from empdept_mv
  2  /

DEPT_ROWID         EMP_ROWID              DEPTNO
------------------ ------------------ ----------
AAARhmAAEAAAAI/AAB AAARhlAAEAAAAI3AAA         20
AAARhmAAEAAAAI/AAC AAARhlAAEAAAAI3AAB         30
AAARhmAAEAAAAI/AAC AAARhlAAEAAAAI3AAC         30
AAARhmAAEAAAAI/AAB AAARhlAAEAAAAI3AAD         20
AAARhmAAEAAAAI/AAC AAARhlAAEAAAAI3AAE         30
AAARhmAAEAAAAI/AAC AAARhlAAEAAAAI3AAF         30
AAARhmAAEAAAAI/AAA AAARhlAAEAAAAI3AAG         10
AAARhmAAEAAAAI/AAB AAARhlAAEAAAAI3AAH         20
AAARhmAAEAAAAI/AAA AAARhlAAEAAAAI3AAI         10
AAARhmAAEAAAAI/AAC AAARhlAAEAAAAI3AAJ         30
AAARhmAAEAAAAI/AAB AAARhlAAEAAAAI3AAK         20
AAARhmAAEAAAAI/AAC AAARhlAAEAAAAI3AAL         30
AAARhmAAEAAAAI/AAB AAARhlAAEAAAAI3AAM         20
AAARhmAAEAAAAI/AAA AAARhlAAEAAAAI3AAN         10
AAARhmAAEAAAAI/AAD                            40

15 rows selected.

SQL> insert into dept values (50,'IT','UTRECHT')
  2  /

1 row created.

SQL> commit
  2  /

Commit complete.

SQL> select * from empdept_mv
  2  /

DEPT_ROWID         EMP_ROWID              DEPTNO
------------------ ------------------ ----------
AAARhmAAEAAAAI/AAB AAARhlAAEAAAAI3AAA         20
AAARhmAAEAAAAI/AAC AAARhlAAEAAAAI3AAB         30
AAARhmAAEAAAAI/AAC AAARhlAAEAAAAI3AAC         30
AAARhmAAEAAAAI/AAB AAARhlAAEAAAAI3AAD         20
AAARhmAAEAAAAI/AAC AAARhlAAEAAAAI3AAE         30
AAARhmAAEAAAAI/AAC AAARhlAAEAAAAI3AAF         30
AAARhmAAEAAAAI/AAA AAARhlAAEAAAAI3AAG         10
AAARhmAAEAAAAI/AAB AAARhlAAEAAAAI3AAH         20
AAARhmAAEAAAAI/AAA AAARhlAAEAAAAI3AAI         10
AAARhmAAEAAAAI/AAC AAARhlAAEAAAAI3AAJ         30
AAARhmAAEAAAAI/AAB AAARhlAAEAAAAI3AAK         20
AAARhmAAEAAAAI/AAC AAARhlAAEAAAAI3AAL         30
AAARhmAAEAAAAI/AAB AAARhlAAEAAAAI3AAM         20
AAARhmAAEAAAAI/AAA AAARhlAAEAAAAI3AAN         10
AAARhmAAEAAAAI/AAD                            40
AAARhmAAEAAAAI7AAA                            50

16 rows selected.

Ограничението за синтаксис на ANSI-join е споменато в точка 6 в това публикация в блог .

Поздрави, Роб.