oracle - ORACLE：使用 LEFT JOIN 时物化视图不起作用

Question

我想从 2 个表的 LEFT JOIN 创建一个 MATERIALIZED VIEW。但是，以下给了我一个错误：

    SELECT field1 
     FROM table_1 a 
     LEFT JOIN table_2 b 
     ON a.field1=b.field2

ORA-12054: 无法为实体化视图设置 ON COMMIT 刷新属性

但是，以下工作：

SELECT field1 
 FROM table_1 a, table_2 b 
 WHERE a.field1=b.field2

有谁知道为什么会这样。

谢谢帮助

Answer 1

要使物化视图快速刷新，有两个条件不满足。第一个是您没有指定所涉及的每个表的 rowid 列。第二个是未记录的限制：不支持 ANSI 连接。

这是一个示例，DEPT 为 table_1，别名 a，EMP 为 table_2，别名 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

这模仿了你的情况。首先添加rowid的：

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

由于 ANSI 连接，它仍然无法快速刷新。转换为旧式外连接语法：

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.

并证明它有效：

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.

本博文的第 6 点提到了 ANSI-join 语法限制。

问候，罗布。

Answer 2

由于这是一个旧帖子；没有提到完整的解决方案。

1. 如 Oracle 文档中所述，外部连接的表应具有主键。
2. 查询不应有任何其他约束，即WHERE子句中不应有任何过滤条件，只有联接；子句中也不能有CASE/DECODE语句SELECT；GROUP BY, SUM(),COUNT()等都是允许的。

在上面的示例中，如果在 dept id 列的部门表上创建主键，则查询将起作用。

Answer 3

按照以下说明使 DBMS_MVIEW.EXPLAIN_MVIEW 工作： http ://www.sqlsnippets.com/en/topic-12884.html

能够：

REFRESH_COMPLETE

不具备：

REFRESH_FAST

此类型 MV 不支持 FROM 列表中的 REFRESH_FAST_AFTER_INSERT内联视图或子查询

此类型 MV 不支持 FROM 列表中的 REFRESH_FAST_AFTER_INSERT内联视图或子查询

REFRESH_FAST_AFTER_INSERT
视图或列表中的子查询

REFRESH_FAST_AFTER_ONETAB_DML
查看禁用 REFRESH_FAST_AFTER_INSERT 的原因

MV_REPORT

REFRESH_FAST_AFTER_ANY_DML
查看禁用 REFRESH_FAST_AFTER_ONETAB_DML 的原因